diff --git a/src/tint/ast/struct_member_offset_attribute.cc b/src/tint/ast/struct_member_offset_attribute.cc
index 48d73336b3..8b9faabaf8 100644
--- a/src/tint/ast/struct_member_offset_attribute.cc
+++ b/src/tint/ast/struct_member_offset_attribute.cc
@@ -25,8 +25,8 @@ namespace tint::ast {
 StructMemberOffsetAttribute::StructMemberOffsetAttribute(ProgramID pid,
                                                          NodeID nid,
                                                          const Source& src,
-                                                         uint32_t o)
-    : Base(pid, nid, src), offset(o) {}
+                                                         const ast::Expression* exp)
+    : Base(pid, nid, src), expr(exp) {}
 
 StructMemberOffsetAttribute::~StructMemberOffsetAttribute() = default;
 
@@ -37,7 +37,8 @@ std::string StructMemberOffsetAttribute::Name() const {
 const StructMemberOffsetAttribute* StructMemberOffsetAttribute::Clone(CloneContext* ctx) const {
     // Clone arguments outside of create() call to have deterministic ordering
     auto src = ctx->Clone(source);
-    return ctx->dst->create<StructMemberOffsetAttribute>(src, offset);
+    auto expr_ = ctx->Clone(expr);
+    return ctx->dst->create<StructMemberOffsetAttribute>(src, expr_);
 }
 
 }  // namespace tint::ast
diff --git a/src/tint/ast/struct_member_offset_attribute.h b/src/tint/ast/struct_member_offset_attribute.h
index 790927eaa8..632d71ae9b 100644
--- a/src/tint/ast/struct_member_offset_attribute.h
+++ b/src/tint/ast/struct_member_offset_attribute.h
@@ -18,6 +18,7 @@
 #include <string>
 
 #include "src/tint/ast/attribute.h"
+#include "src/tint/ast/expression.h"
 
 namespace tint::ast {
 
@@ -37,8 +38,11 @@ class StructMemberOffsetAttribute final : public Castable<StructMemberOffsetAttr
     /// @param pid the identifier of the program that owns this node
     /// @param nid the unique node identifier
     /// @param src the source of this node
-    /// @param offset the offset value
-    StructMemberOffsetAttribute(ProgramID pid, NodeID nid, const Source& src, uint32_t offset);
+    /// @param expr the offset expression
+    StructMemberOffsetAttribute(ProgramID pid,
+                                NodeID nid,
+                                const Source& src,
+                                const ast::Expression* expr);
     ~StructMemberOffsetAttribute() override;
 
     /// @returns the WGSL name for the attribute
@@ -50,8 +54,8 @@ class StructMemberOffsetAttribute final : public Castable<StructMemberOffsetAttr
     /// @return the newly cloned node
     const StructMemberOffsetAttribute* Clone(CloneContext* ctx) const override;
 
-    /// The offset value
-    const uint32_t offset;
+    /// The offset expression
+    const ast::Expression* const expr;
 };
 
 }  // namespace tint::ast
diff --git a/src/tint/ast/struct_member_offset_attribute_test.cc b/src/tint/ast/struct_member_offset_attribute_test.cc
index 9d81ffb1c4..23dd697cfd 100644
--- a/src/tint/ast/struct_member_offset_attribute_test.cc
+++ b/src/tint/ast/struct_member_offset_attribute_test.cc
@@ -17,11 +17,13 @@
 namespace tint::ast {
 namespace {
 
+using namespace tint::number_suffixes;  // NOLINT
 using StructMemberOffsetAttributeTest = TestHelper;
 
 TEST_F(StructMemberOffsetAttributeTest, Creation) {
-    auto* d = create<StructMemberOffsetAttribute>(2u);
-    EXPECT_EQ(2u, d->offset);
+    auto* d = MemberOffset(2_u);
+    ASSERT_TRUE(d->expr->Is<ast::IntLiteralExpression>());
+    EXPECT_EQ(2u, d->expr->As<ast::IntLiteralExpression>()->value);
 }
 
 }  // namespace
diff --git a/src/tint/ast/struct_member_size_attribute.cc b/src/tint/ast/struct_member_size_attribute.cc
index 391907877d..833896decd 100644
--- a/src/tint/ast/struct_member_size_attribute.cc
+++ b/src/tint/ast/struct_member_size_attribute.cc
@@ -26,8 +26,8 @@ namespace tint::ast {
 StructMemberSizeAttribute::StructMemberSizeAttribute(ProgramID pid,
                                                      NodeID nid,
                                                      const Source& src,
-                                                     uint32_t sz)
-    : Base(pid, nid, src), size(sz) {}
+                                                     const ast::Expression* exp)
+    : Base(pid, nid, src), expr(exp) {}
 
 StructMemberSizeAttribute::~StructMemberSizeAttribute() = default;
 
@@ -38,7 +38,8 @@ std::string StructMemberSizeAttribute::Name() const {
 const StructMemberSizeAttribute* StructMemberSizeAttribute::Clone(CloneContext* ctx) const {
     // Clone arguments outside of create() call to have deterministic ordering
     auto src = ctx->Clone(source);
-    return ctx->dst->create<StructMemberSizeAttribute>(src, size);
+    auto expr_ = ctx->Clone(expr);
+    return ctx->dst->create<StructMemberSizeAttribute>(src, expr_);
 }
 
 }  // namespace tint::ast
diff --git a/src/tint/ast/struct_member_size_attribute.h b/src/tint/ast/struct_member_size_attribute.h
index 5649e2eaa3..c048b1fd1a 100644
--- a/src/tint/ast/struct_member_size_attribute.h
+++ b/src/tint/ast/struct_member_size_attribute.h
@@ -19,6 +19,7 @@
 #include <string>
 
 #include "src/tint/ast/attribute.h"
+#include "src/tint/ast/expression.h"
 
 namespace tint::ast {
 
@@ -29,8 +30,11 @@ class StructMemberSizeAttribute final : public Castable<StructMemberSizeAttribut
     /// @param pid the identifier of the program that owns this node
     /// @param nid the unique node identifier
     /// @param src the source of this node
-    /// @param size the size value
-    StructMemberSizeAttribute(ProgramID pid, NodeID nid, const Source& src, uint32_t size);
+    /// @param expr the size expression
+    StructMemberSizeAttribute(ProgramID pid,
+                              NodeID nid,
+                              const Source& src,
+                              const ast::Expression* expr);
     ~StructMemberSizeAttribute() override;
 
     /// @returns the WGSL name for the attribute
@@ -42,8 +46,8 @@ class StructMemberSizeAttribute final : public Castable<StructMemberSizeAttribut
     /// @return the newly cloned node
     const StructMemberSizeAttribute* Clone(CloneContext* ctx) const override;
 
-    /// The size value
-    const uint32_t size;
+    /// The size expression
+    const ast::Expression* const expr;
 };
 
 }  // namespace tint::ast
diff --git a/src/tint/ast/struct_member_size_attribute_test.cc b/src/tint/ast/struct_member_size_attribute_test.cc
index a82d53a0b0..9f6b49bf3f 100644
--- a/src/tint/ast/struct_member_size_attribute_test.cc
+++ b/src/tint/ast/struct_member_size_attribute_test.cc
@@ -19,11 +19,13 @@
 namespace tint::ast {
 namespace {
 
+using namespace tint::number_suffixes;  // NOLINT
 using StructMemberSizeAttributeTest = TestHelper;
 
 TEST_F(StructMemberSizeAttributeTest, Creation) {
-    auto* d = create<StructMemberSizeAttribute>(2u);
-    EXPECT_EQ(2u, d->size);
+    auto* d = MemberSize(2_u);
+    ASSERT_TRUE(d->expr->Is<ast::IntLiteralExpression>());
+    EXPECT_EQ(2u, d->expr->As<ast::IntLiteralExpression>()->value);
 }
 
 }  // namespace
diff --git a/src/tint/ast/struct_member_test.cc b/src/tint/ast/struct_member_test.cc
index 69772f4e14..850be9fbd4 100644
--- a/src/tint/ast/struct_member_test.cc
+++ b/src/tint/ast/struct_member_test.cc
@@ -18,10 +18,11 @@
 namespace tint::ast {
 namespace {
 
+using namespace tint::number_suffixes;  // NOLINT
 using StructMemberTest = TestHelper;
 
 TEST_F(StructMemberTest, Creation) {
-    auto* st = Member("a", ty.i32(), utils::Vector{MemberSize(4)});
+    auto* st = Member("a", ty.i32(), utils::Vector{MemberSize(4_a)});
     EXPECT_EQ(st->symbol, Symbol(1, ID()));
     EXPECT_TRUE(st->type->Is<ast::I32>());
     EXPECT_EQ(st->attributes.Length(), 1u);
@@ -66,7 +67,7 @@ TEST_F(StructMemberTest, Assert_Null_Attribute) {
     EXPECT_FATAL_FAILURE(
         {
             ProgramBuilder b;
-            b.Member("a", b.ty.i32(), utils::Vector{b.MemberSize(4), nullptr});
+            b.Member("a", b.ty.i32(), utils::Vector{b.MemberSize(4_a), nullptr});
         },
         "internal compiler error");
 }
@@ -76,7 +77,7 @@ TEST_F(StructMemberTest, Assert_DifferentProgramID_Symbol) {
         {
             ProgramBuilder b1;
             ProgramBuilder b2;
-            b1.Member(b2.Sym("a"), b1.ty.i32(), utils::Vector{b1.MemberSize(4)});
+            b1.Member(b2.Sym("a"), b1.ty.i32(), utils::Vector{b1.MemberSize(4_a)});
         },
         "internal compiler error");
 }
@@ -86,7 +87,7 @@ TEST_F(StructMemberTest, Assert_DifferentProgramID_Attribute) {
         {
             ProgramBuilder b1;
             ProgramBuilder b2;
-            b1.Member("a", b1.ty.i32(), utils::Vector{b2.MemberSize(4)});
+            b1.Member("a", b1.ty.i32(), utils::Vector{b2.MemberSize(4_a)});
         },
         "internal compiler error");
 }
diff --git a/src/tint/program_builder.h b/src/tint/program_builder.h
index ead13e9c9f..c94f5fbd86 100644
--- a/src/tint/program_builder.h
+++ b/src/tint/program_builder.h
@@ -2251,25 +2251,37 @@ class ProgramBuilder {
     }
 
     /// Creates a ast::StructMemberOffsetAttribute
-    /// @param val the offset value
+    /// @param val the offset expression
     /// @returns the offset attribute pointer
-    const ast::StructMemberOffsetAttribute* MemberOffset(uint32_t val) {
-        return create<ast::StructMemberOffsetAttribute>(source_, val);
+    template <typename EXPR>
+    const ast::StructMemberOffsetAttribute* MemberOffset(EXPR&& val) {
+        return create<ast::StructMemberOffsetAttribute>(source_, Expr(std::forward<EXPR>(val)));
+    }
+
+    /// Creates a ast::StructMemberOffsetAttribute
+    /// @param source the source information
+    /// @param val the offset expression
+    /// @returns the offset attribute pointer
+    template <typename EXPR>
+    const ast::StructMemberOffsetAttribute* MemberOffset(const Source& source, EXPR&& val) {
+        return create<ast::StructMemberOffsetAttribute>(source, Expr(std::forward<EXPR>(val)));
     }
 
     /// Creates a ast::StructMemberSizeAttribute
     /// @param source the source information
     /// @param val the size value
     /// @returns the size attribute pointer
-    const ast::StructMemberSizeAttribute* MemberSize(const Source& source, uint32_t val) {
-        return create<ast::StructMemberSizeAttribute>(source, val);
+    template <typename EXPR>
+    const ast::StructMemberSizeAttribute* MemberSize(const Source& source, EXPR&& val) {
+        return create<ast::StructMemberSizeAttribute>(source, Expr(std::forward<EXPR>(val)));
     }
 
     /// Creates a ast::StructMemberSizeAttribute
     /// @param val the size value
     /// @returns the size attribute pointer
-    const ast::StructMemberSizeAttribute* MemberSize(uint32_t val) {
-        return create<ast::StructMemberSizeAttribute>(source_, val);
+    template <typename EXPR>
+    const ast::StructMemberSizeAttribute* MemberSize(EXPR&& val) {
+        return create<ast::StructMemberSizeAttribute>(source_, Expr(std::forward<EXPR>(val)));
     }
 
     /// Creates a ast::StructMemberAlignAttribute
@@ -2525,7 +2537,7 @@ class ProgramBuilder {
     const ast::StructMember* Member(uint32_t offset, NAME&& name, const ast::Type* type) {
         return create<ast::StructMember>(source_, Sym(std::forward<NAME>(name)), type,
                                          utils::Vector<const ast::Attribute*, 1>{
-                                             create<ast::StructMemberOffsetAttribute>(offset),
+                                             MemberOffset(AInt(offset)),
                                          });
     }
 
diff --git a/src/tint/reader/spirv/parser_impl.cc b/src/tint/reader/spirv/parser_impl.cc
index 37ea5ca3f3..caa2c69173 100644
--- a/src/tint/reader/spirv/parser_impl.cc
+++ b/src/tint/reader/spirv/parser_impl.cc
@@ -464,7 +464,7 @@ ParserImpl::AttributeList ParserImpl::ConvertMemberDecoration(uint32_t struct_ty
                 return {};
             }
             return {
-                create<ast::StructMemberOffsetAttribute>(Source{}, decoration[1]),
+                builder_.MemberOffset(Source{}, AInt(decoration[1])),
             };
         case SpvDecorationNonReadable:
             // WGSL doesn't have a member decoration for this.  Silently drop it.
diff --git a/src/tint/reader/spirv/parser_impl_convert_member_decoration_test.cc b/src/tint/reader/spirv/parser_impl_convert_member_decoration_test.cc
index cd3e7b5002..767b3337d4 100644
--- a/src/tint/reader/spirv/parser_impl_convert_member_decoration_test.cc
+++ b/src/tint/reader/spirv/parser_impl_convert_member_decoration_test.cc
@@ -54,7 +54,8 @@ TEST_F(SpvParserTest, ConvertMemberDecoration_Offset) {
     EXPECT_TRUE(result[0]->Is<ast::StructMemberOffsetAttribute>());
     auto* offset_deco = result[0]->As<ast::StructMemberOffsetAttribute>();
     ASSERT_NE(offset_deco, nullptr);
-    EXPECT_EQ(offset_deco->offset, 8u);
+    ASSERT_TRUE(offset_deco->expr->Is<ast::IntLiteralExpression>());
+    EXPECT_EQ(offset_deco->expr->As<ast::IntLiteralExpression>()->value, 8u);
     EXPECT_TRUE(p->error().empty());
 }
 
diff --git a/src/tint/reader/wgsl/parser_impl.cc b/src/tint/reader/wgsl/parser_impl.cc
index f3b424e71b..2c72d6a0c3 100644
--- a/src/tint/reader/wgsl/parser_impl.cc
+++ b/src/tint/reader/wgsl/parser_impl.cc
@@ -3566,7 +3566,7 @@ Maybe<const ast::Attribute*> ParserImpl::attribute() {
             }
             match(Token::Type::kComma);
 
-            return create<ast::StructMemberSizeAttribute>(t.source(), val.value);
+            return builder_.MemberSize(t.source(), AInt(val.value));
         });
     }
 
diff --git a/src/tint/reader/wgsl/parser_impl_struct_member_attribute_test.cc b/src/tint/reader/wgsl/parser_impl_struct_member_attribute_test.cc
index cc6d186d32..9bafaf0f44 100644
--- a/src/tint/reader/wgsl/parser_impl_struct_member_attribute_test.cc
+++ b/src/tint/reader/wgsl/parser_impl_struct_member_attribute_test.cc
@@ -30,7 +30,8 @@ TEST_F(ParserImplTest, Attribute_Size) {
     ASSERT_TRUE(member_attr->Is<ast::StructMemberSizeAttribute>());
 
     auto* o = member_attr->As<ast::StructMemberSizeAttribute>();
-    EXPECT_EQ(o->size, 4u);
+    ASSERT_TRUE(o->expr->Is<ast::IntLiteralExpression>());
+    EXPECT_EQ(o->expr->As<ast::IntLiteralExpression>()->value, 4u);
 }
 
 TEST_F(ParserImplTest, Attribute_Size_TrailingComma) {
@@ -46,7 +47,8 @@ TEST_F(ParserImplTest, Attribute_Size_TrailingComma) {
     ASSERT_TRUE(member_attr->Is<ast::StructMemberSizeAttribute>());
 
     auto* o = member_attr->As<ast::StructMemberSizeAttribute>();
-    EXPECT_EQ(o->size, 4u);
+    ASSERT_TRUE(o->expr->Is<ast::IntLiteralExpression>());
+    EXPECT_EQ(o->expr->As<ast::IntLiteralExpression>()->value, 4u);
 }
 
 TEST_F(ParserImplTest, Attribute_Size_MissingLeftParen) {
diff --git a/src/tint/reader/wgsl/parser_impl_struct_member_test.cc b/src/tint/reader/wgsl/parser_impl_struct_member_test.cc
index fe233fe8a4..6267406571 100644
--- a/src/tint/reader/wgsl/parser_impl_struct_member_test.cc
+++ b/src/tint/reader/wgsl/parser_impl_struct_member_test.cc
@@ -73,8 +73,11 @@ TEST_F(ParserImplTest, StructMember_ParsesWithSizeAttribute) {
     EXPECT_EQ(m->symbol, builder.Symbols().Get("a"));
     EXPECT_TRUE(m->type->Is<ast::I32>());
     EXPECT_EQ(m->attributes.Length(), 1u);
-    EXPECT_TRUE(m->attributes[0]->Is<ast::StructMemberSizeAttribute>());
-    EXPECT_EQ(m->attributes[0]->As<ast::StructMemberSizeAttribute>()->size, 2u);
+    ASSERT_TRUE(m->attributes[0]->Is<ast::StructMemberSizeAttribute>());
+    auto* s = m->attributes[0]->As<ast::StructMemberSizeAttribute>();
+
+    ASSERT_TRUE(s->expr->Is<ast::IntLiteralExpression>());
+    EXPECT_EQ(s->expr->As<ast::IntLiteralExpression>()->value, 2u);
 
     EXPECT_EQ(m->source.range, (Source::Range{{1u, 10u}, {1u, 11u}}));
     EXPECT_EQ(m->type->source.range, (Source::Range{{1u, 14u}, {1u, 17u}}));
@@ -95,7 +98,9 @@ TEST_F(ParserImplTest, StructMember_ParsesWithMultipleattributes) {
     EXPECT_TRUE(m->type->Is<ast::I32>());
     EXPECT_EQ(m->attributes.Length(), 2u);
     ASSERT_TRUE(m->attributes[0]->Is<ast::StructMemberSizeAttribute>());
-    EXPECT_EQ(m->attributes[0]->As<ast::StructMemberSizeAttribute>()->size, 2u);
+    auto* size_attr = m->attributes[0]->As<ast::StructMemberSizeAttribute>();
+    ASSERT_TRUE(size_attr->expr->Is<ast::IntLiteralExpression>());
+    EXPECT_EQ(size_attr->expr->As<ast::IntLiteralExpression>()->value, 2u);
 
     ASSERT_TRUE(m->attributes[1]->Is<ast::StructMemberAlignAttribute>());
     auto* attr = m->attributes[1]->As<ast::StructMemberAlignAttribute>();
diff --git a/src/tint/resolver/attribute_validation_test.cc b/src/tint/resolver/attribute_validation_test.cc
index b182f6d85e..e648562012 100644
--- a/src/tint/resolver/attribute_validation_test.cc
+++ b/src/tint/resolver/attribute_validation_test.cc
@@ -106,9 +106,9 @@ static utils::Vector<const ast::Attribute*, 2> createAttributes(const Source& so
         case AttributeKind::kLocation:
             return {builder.Location(source, 1_a)};
         case AttributeKind::kOffset:
-            return {builder.create<ast::StructMemberOffsetAttribute>(source, 4u)};
+            return {builder.MemberOffset(source, 4_a)};
         case AttributeKind::kSize:
-            return {builder.create<ast::StructMemberSizeAttribute>(source, 16u)};
+            return {builder.MemberSize(source, 16_a)};
         case AttributeKind::kStage:
             return {builder.Stage(source, ast::PipelineStage::kCompute)};
         case AttributeKind::kStride:
diff --git a/src/tint/resolver/resolver.cc b/src/tint/resolver/resolver.cc
index 27dc2199b8..911b66c3e7 100644
--- a/src/tint/resolver/resolver.cc
+++ b/src/tint/resolver/resolver.cc
@@ -2803,11 +2803,22 @@ sem::Struct* Resolver::Structure(const ast::Struct* str) {
             if (auto* o = attr->As<ast::StructMemberOffsetAttribute>()) {
                 // Offset attributes are not part of the WGSL spec, but are emitted
                 // by the SPIR-V reader.
-                if (o->offset < struct_size) {
+
+                auto* materialized = Materialize(Expression(o->expr));
+                if (!materialized) {
+                    return nullptr;
+                }
+                auto const_value = materialized->ConstantValue();
+                if (!const_value) {
+                    AddError("'offset' must be constant expression", o->expr->source);
+                    return nullptr;
+                }
+                offset = const_value->As<uint64_t>();
+
+                if (offset < struct_size) {
                     AddError("offsets must be in ascending order", o->source);
                     return nullptr;
                 }
-                offset = o->offset;
                 align = 1;
                 has_offset_attr = true;
             } else if (auto* a = attr->As<ast::StructMemberAlignAttribute>()) {
@@ -2829,13 +2840,24 @@ sem::Struct* Resolver::Structure(const ast::Struct* str) {
                 align = const_value->As<u32>();
                 has_align_attr = true;
             } else if (auto* s = attr->As<ast::StructMemberSizeAttribute>()) {
-                if (s->size < size) {
+                auto* materialized = Materialize(Expression(s->expr));
+                if (!materialized) {
+                    return nullptr;
+                }
+                auto const_value = materialized->ConstantValue();
+                if (!const_value) {
+                    AddError("'size' must be constant expression", s->expr->source);
+                    return nullptr;
+                }
+                auto value = const_value->As<uint64_t>();
+
+                if (value < size) {
                     AddError("size must be at least as big as the type's size (" +
                                  std::to_string(size) + ")",
                              s->source);
                     return nullptr;
                 }
-                size = s->size;
+                size = const_value->As<u32>();
                 has_size_attr = true;
             } else if (auto* l = attr->As<ast::LocationAttribute>()) {
                 auto* materialize = Materialize(Expression(l->expr));
diff --git a/src/tint/resolver/storage_class_layout_validation_test.cc b/src/tint/resolver/storage_class_layout_validation_test.cc
index 8f1b2c1c37..91d0d5d021 100644
--- a/src/tint/resolver/storage_class_layout_validation_test.cc
+++ b/src/tint/resolver/storage_class_layout_validation_test.cc
@@ -35,7 +35,7 @@ TEST_F(ResolverStorageClassLayoutValidationTest, StorageBuffer_UnalignedMember)
 
     Structure(Source{{12, 34}}, "S",
               utils::Vector{
-                  Member("a", ty.f32(), utils::Vector{MemberSize(5)}),
+                  Member("a", ty.f32(), utils::Vector{MemberSize(5_a)}),
                   Member(Source{{34, 56}}, "b", ty.f32(), utils::Vector{MemberAlign(1_u)}),
               });
 
@@ -65,7 +65,7 @@ TEST_F(ResolverStorageClassLayoutValidationTest, StorageBuffer_UnalignedMember_S
 
     Structure(Source{{12, 34}}, "S",
               utils::Vector{
-                  Member("a", ty.f32(), utils::Vector{MemberSize(5)}),
+                  Member("a", ty.f32(), utils::Vector{MemberSize(5_a)}),
                   Member(Source{{34, 56}}, "b", ty.f32(), utils::Vector{MemberAlign(4_u)}),
               });
 
@@ -227,7 +227,7 @@ TEST_F(ResolverStorageClassLayoutValidationTest, UniformBuffer_MembersOffsetNotM
 
     Structure(Source{{12, 34}}, "Inner",
               utils::Vector{
-                  Member("scalar", ty.i32(), utils::Vector{MemberAlign(1_u), MemberSize(5)}),
+                  Member("scalar", ty.i32(), utils::Vector{MemberAlign(1_u), MemberSize(5_a)}),
               });
 
     Structure(Source{{34, 56}}, "Outer",
@@ -279,7 +279,7 @@ TEST_F(ResolverStorageClassLayoutValidationTest,
                   Member("a", ty.i32()),
                   Member("b", ty.i32()),
                   Member("c", ty.i32()),
-                  Member("scalar", ty.i32(), utils::Vector{MemberAlign(1_u), MemberSize(5)}),
+                  Member("scalar", ty.i32(), utils::Vector{MemberAlign(1_u), MemberSize(5_a)}),
               });
 
     Structure(Source{{34, 56}}, "Outer",
@@ -327,7 +327,7 @@ TEST_F(ResolverStorageClassLayoutValidationTest,
 
     Structure(Source{{12, 34}}, "Inner",
               utils::Vector{
-                  Member("scalar", ty.i32(), utils::Vector{MemberAlign(1_u), MemberSize(5)}),
+                  Member("scalar", ty.i32(), utils::Vector{MemberAlign(1_u), MemberSize(5_a)}),
               });
 
     Structure(Source{{34, 56}}, "Outer",
@@ -550,7 +550,7 @@ TEST_F(ResolverStorageClassLayoutValidationTest, PushConstant_UnalignedMember) {
     Enable(ast::Extension::kChromiumExperimentalPushConstant);
     Structure(
         Source{{12, 34}}, "S",
-        utils::Vector{Member("a", ty.f32(), utils::Vector{MemberSize(5)}),
+        utils::Vector{Member("a", ty.f32(), utils::Vector{MemberSize(5_a)}),
                       Member(Source{{34, 56}}, "b", ty.f32(), utils::Vector{MemberAlign(1_u)})});
     GlobalVar(Source{{78, 90}}, "a", ty.type_name("S"), ast::StorageClass::kPushConstant);
 
@@ -575,7 +575,7 @@ TEST_F(ResolverStorageClassLayoutValidationTest, PushConstant_Aligned) {
     // };
     // var<push_constant> a : S;
     Enable(ast::Extension::kChromiumExperimentalPushConstant);
-    Structure("S", utils::Vector{Member("a", ty.f32(), utils::Vector{MemberSize(5)}),
+    Structure("S", utils::Vector{Member("a", ty.f32(), utils::Vector{MemberSize(5_a)}),
                                  Member("b", ty.f32(), utils::Vector{MemberAlign(4_u)})});
     GlobalVar("a", ty.type_name("S"), ast::StorageClass::kPushConstant);
 
diff --git a/src/tint/resolver/storage_class_validation_test.cc b/src/tint/resolver/storage_class_validation_test.cc
index 8c1a253c4f..cff20c0923 100644
--- a/src/tint/resolver/storage_class_validation_test.cc
+++ b/src/tint/resolver/storage_class_validation_test.cc
@@ -400,7 +400,7 @@ TEST_F(ResolverStorageClassValidationTest, UniformBufferArrayF16_TemporallyBan)
     Enable(ast::Extension::kF16);
 
     auto* s = Structure(
-        "S", utils::Vector{Member("a", ty.f16(Source{{56, 78}}), utils::Vector{MemberSize(16)})});
+        "S", utils::Vector{Member("a", ty.f16(Source{{56, 78}}), utils::Vector{MemberSize(16_a)})});
     auto* a = ty.array(ty.Of(s), 3_u);
     GlobalVar("g", a, ast::StorageClass::kUniform, Binding(0_a), Group(0_a));
 
@@ -474,7 +474,7 @@ TEST_F(ResolverStorageClassValidationTest, UniformBufferArrayF32) {
     //   @size(16) f : f32;
     // }
     // var<uniform> g : array<S, 3u>;
-    auto* s = Structure("S", utils::Vector{Member("a", ty.f32(), utils::Vector{MemberSize(16)})});
+    auto* s = Structure("S", utils::Vector{Member("a", ty.f32(), utils::Vector{MemberSize(16_a)})});
     auto* a = ty.array(ty.Of(s), 3_u);
     GlobalVar(Source{{56, 78}}, "g", a, ast::StorageClass::kUniform, Binding(0_a), Group(0_a));
 
diff --git a/src/tint/resolver/struct_layout_test.cc b/src/tint/resolver/struct_layout_test.cc
index ae3972b04f..5b5ab686e8 100644
--- a/src/tint/resolver/struct_layout_test.cc
+++ b/src/tint/resolver/struct_layout_test.cc
@@ -460,15 +460,15 @@ TEST_F(ResolverStructLayoutTest, NestedStruct) {
 
 TEST_F(ResolverStructLayoutTest, SizeAttributes) {
     auto* inner = Structure("Inner", utils::Vector{
-                                         Member("a", ty.f32(), utils::Vector{MemberSize(8)}),
-                                         Member("b", ty.f32(), utils::Vector{MemberSize(16)}),
-                                         Member("c", ty.f32(), utils::Vector{MemberSize(8)}),
+                                         Member("a", ty.f32(), utils::Vector{MemberSize(8_a)}),
+                                         Member("b", ty.f32(), utils::Vector{MemberSize(16_a)}),
+                                         Member("c", ty.f32(), utils::Vector{MemberSize(8_a)}),
                                      });
     auto* s = Structure("S", utils::Vector{
-                                 Member("a", ty.f32(), utils::Vector{MemberSize(4)}),
-                                 Member("b", ty.u32(), utils::Vector{MemberSize(8)}),
+                                 Member("a", ty.f32(), utils::Vector{MemberSize(4_a)}),
+                                 Member("b", ty.u32(), utils::Vector{MemberSize(8_a)}),
                                  Member("c", ty.Of(inner)),
-                                 Member("d", ty.i32(), utils::Vector{MemberSize(32)}),
+                                 Member("d", ty.i32(), utils::Vector{MemberSize(32_a)}),
                              });
 
     ASSERT_TRUE(r()->Resolve()) << r()->error();
diff --git a/src/tint/resolver/validation_test.cc b/src/tint/resolver/validation_test.cc
index 6054cacf4b..90b1664615 100644
--- a/src/tint/resolver/validation_test.cc
+++ b/src/tint/resolver/validation_test.cc
@@ -1257,7 +1257,7 @@ TEST_F(ResolverValidationTest, ZeroStructMemberAlignAttribute) {
 
 TEST_F(ResolverValidationTest, ZeroStructMemberSizeAttribute) {
     Structure("S", utils::Vector{
-                       Member("a", ty.f32(), utils::Vector{MemberSize(Source{{12, 34}}, 0)}),
+                       Member("a", ty.f32(), utils::Vector{MemberSize(Source{{12, 34}}, 0_a)}),
                    });
 
     EXPECT_FALSE(r()->Resolve());
@@ -1267,7 +1267,7 @@ TEST_F(ResolverValidationTest, ZeroStructMemberSizeAttribute) {
 TEST_F(ResolverValidationTest, OffsetAndSizeAttribute) {
     Structure("S", utils::Vector{
                        Member(Source{{12, 34}}, "a", ty.f32(),
-                              utils::Vector{MemberOffset(0), MemberSize(4)}),
+                              utils::Vector{MemberOffset(0_a), MemberSize(4_a)}),
                    });
 
     EXPECT_FALSE(r()->Resolve());
@@ -1279,7 +1279,7 @@ TEST_F(ResolverValidationTest, OffsetAndSizeAttribute) {
 TEST_F(ResolverValidationTest, OffsetAndAlignAttribute) {
     Structure("S", utils::Vector{
                        Member(Source{{12, 34}}, "a", ty.f32(),
-                              utils::Vector{MemberOffset(0), MemberAlign(4_u)}),
+                              utils::Vector{MemberOffset(0_a), MemberAlign(4_u)}),
                    });
 
     EXPECT_FALSE(r()->Resolve());
@@ -1291,7 +1291,7 @@ TEST_F(ResolverValidationTest, OffsetAndAlignAttribute) {
 TEST_F(ResolverValidationTest, OffsetAndAlignAndSizeAttribute) {
     Structure("S", utils::Vector{
                        Member(Source{{12, 34}}, "a", ty.f32(),
-                              utils::Vector{MemberOffset(0), MemberAlign(4_u), MemberSize(4)}),
+                              utils::Vector{MemberOffset(0_a), MemberAlign(4_u), MemberSize(4_a)}),
                    });
 
     EXPECT_FALSE(r()->Resolve());
diff --git a/src/tint/transform/decompose_strided_array.cc b/src/tint/transform/decompose_strided_array.cc
index 61841f6299..b7fe53c360 100644
--- a/src/tint/transform/decompose_strided_array.cc
+++ b/src/tint/transform/decompose_strided_array.cc
@@ -73,7 +73,7 @@ void DecomposeStridedArray::Run(CloneContext& ctx, const DataMap&, DataMap&) con
                     auto* member_ty = ctx.Clone(ast->type);
                     auto* member = ctx.dst->Member(kMemberName, member_ty,
                                                    utils::Vector{
-                                                       ctx.dst->MemberSize(arr->Stride()),
+                                                       ctx.dst->MemberSize(AInt(arr->Stride())),
                                                    });
                     ctx.dst->Structure(name, utils::Vector{member});
                     return name;
diff --git a/src/tint/transform/decompose_strided_matrix_test.cc b/src/tint/transform/decompose_strided_matrix_test.cc
index c7a8f59534..6bfba7c298 100644
--- a/src/tint/transform/decompose_strided_matrix_test.cc
+++ b/src/tint/transform/decompose_strided_matrix_test.cc
@@ -71,7 +71,7 @@ TEST_F(DecomposeStridedMatrixTest, ReadUniformMatrix) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(16u),
+                              b.MemberOffset(16_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -127,7 +127,7 @@ TEST_F(DecomposeStridedMatrixTest, ReadUniformColumn) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(16u),
+                              b.MemberOffset(16_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -180,7 +180,7 @@ TEST_F(DecomposeStridedMatrixTest, ReadUniformMatrix_DefaultStride) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(16u),
+                              b.MemberOffset(16_u),
                               b.create<ast::StrideAttribute>(8u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -233,7 +233,7 @@ TEST_F(DecomposeStridedMatrixTest, ReadStorageMatrix) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(8u),
+                              b.MemberOffset(8_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -290,7 +290,7 @@ TEST_F(DecomposeStridedMatrixTest, ReadStorageColumn) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(16u),
+                              b.MemberOffset(16_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -344,7 +344,7 @@ TEST_F(DecomposeStridedMatrixTest, WriteStorageMatrix) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(8u),
+                              b.MemberOffset(8_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -402,7 +402,7 @@ TEST_F(DecomposeStridedMatrixTest, WriteStorageColumn) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(8u),
+                              b.MemberOffset(8_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -461,7 +461,7 @@ TEST_F(DecomposeStridedMatrixTest, ReadWriteViaPointerLets) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(8u),
+                              b.MemberOffset(8_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -532,7 +532,7 @@ TEST_F(DecomposeStridedMatrixTest, ReadPrivateMatrix) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(8u),
+                              b.MemberOffset(8_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
@@ -585,7 +585,7 @@ TEST_F(DecomposeStridedMatrixTest, WritePrivateMatrix) {
         "S", utils::Vector{
                  b.Member("m", b.ty.mat2x2<f32>(),
                           utils::Vector{
-                              b.create<ast::StructMemberOffsetAttribute>(8u),
+                              b.MemberOffset(8_u),
                               b.create<ast::StrideAttribute>(32u),
                               b.Disable(ast::DisabledValidation::kIgnoreStrideAttribute),
                           }),
diff --git a/src/tint/transform/std140.cc b/src/tint/transform/std140.cc
index f46fdea5c8..e6f070b255 100644
--- a/src/tint/transform/std140.cc
+++ b/src/tint/transform/std140.cc
@@ -246,9 +246,9 @@ struct Std140::State {
                                     // The matrix was @size() annotated with a larger size than the
                                     // natural size for the matrix. This extra padding needs to be
                                     // applied to the last column vector.
-                                    attributes.Push(
-                                        b.MemberSize(member->Size() - mat->ColumnType()->Size() *
-                                                                          (num_columns - 1)));
+                                    attributes.Push(b.MemberSize(
+                                        AInt(member->Size() -
+                                             mat->ColumnType()->Size() * (num_columns - 1))));
                                 }
 
                                 // Build the member
diff --git a/src/tint/writer/glsl/generator_impl_type_test.cc b/src/tint/writer/glsl/generator_impl_type_test.cc
index 15c139810b..c2d9109a42 100644
--- a/src/tint/writer/glsl/generator_impl_type_test.cc
+++ b/src/tint/writer/glsl/generator_impl_type_test.cc
@@ -212,8 +212,8 @@ TEST_F(GlslGeneratorImplTest_Type, EmitType_Struct_NameCollision) {
 
 TEST_F(GlslGeneratorImplTest_Type, EmitType_Struct_WithOffsetAttributes) {
     auto* s = Structure("S", utils::Vector{
-                                 Member("a", ty.i32(), utils::Vector{MemberOffset(0)}),
-                                 Member("b", ty.f32(), utils::Vector{MemberOffset(8)}),
+                                 Member("a", ty.i32(), utils::Vector{MemberOffset(0_a)}),
+                                 Member("b", ty.f32(), utils::Vector{MemberOffset(8_a)}),
                              });
     GlobalVar("g", ty.Of(s), ast::StorageClass::kPrivate);
 
diff --git a/src/tint/writer/hlsl/generator_impl_type_test.cc b/src/tint/writer/hlsl/generator_impl_type_test.cc
index 279eb3fd10..75dac72d4e 100644
--- a/src/tint/writer/hlsl/generator_impl_type_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_type_test.cc
@@ -221,8 +221,8 @@ TEST_F(HlslGeneratorImplTest_Type, EmitType_Struct_NameCollision) {
 
 TEST_F(HlslGeneratorImplTest_Type, EmitType_Struct_WithOffsetAttributes) {
     auto* s = Structure("S", utils::Vector{
-                                 Member("a", ty.i32(), utils::Vector{MemberOffset(0)}),
-                                 Member("b", ty.f32(), utils::Vector{MemberOffset(8)}),
+                                 Member("a", ty.i32(), utils::Vector{MemberOffset(0_a)}),
+                                 Member("b", ty.f32(), utils::Vector{MemberOffset(8_a)}),
                              });
     GlobalVar("g", ty.Of(s), ast::StorageClass::kPrivate);
 
diff --git a/src/tint/writer/msl/generator_impl_type_test.cc b/src/tint/writer/msl/generator_impl_type_test.cc
index a6901b4cb1..c8f4f6d4df 100644
--- a/src/tint/writer/msl/generator_impl_type_test.cc
+++ b/src/tint/writer/msl/generator_impl_type_test.cc
@@ -254,8 +254,8 @@ TEST_F(MslGeneratorImplTest, EmitType_StructDecl) {
 TEST_F(MslGeneratorImplTest, EmitType_Struct_Layout_NonComposites) {
     auto* s = Structure(
         "S", utils::Vector{
-                 Member("a", ty.i32(), utils::Vector{MemberSize(32)}),
-                 Member("b", ty.f32(), utils::Vector{MemberAlign(128_u), MemberSize(128)}),
+                 Member("a", ty.i32(), utils::Vector{MemberSize(32_a)}),
+                 Member("b", ty.f32(), utils::Vector{MemberAlign(128_u), MemberSize(128_a)}),
                  Member("c", ty.vec2<f32>()),
                  Member("d", ty.u32()),
                  Member("e", ty.vec3<f32>()),
@@ -376,10 +376,11 @@ TEST_F(MslGeneratorImplTest, EmitType_Struct_Layout_Structures) {
                              });
 
     // inner_y: size(516), align(4)
-    auto* inner_y = Structure("inner_y", utils::Vector{
-                                             Member("a", ty.i32(), utils::Vector{MemberSize(512)}),
-                                             Member("b", ty.f32()),
-                                         });
+    auto* inner_y =
+        Structure("inner_y", utils::Vector{
+                                 Member("a", ty.i32(), utils::Vector{MemberSize(512_a)}),
+                                 Member("b", ty.f32()),
+                             });
 
     auto* s = Structure("S", utils::Vector{
                                  Member("a", ty.i32()),
@@ -595,7 +596,7 @@ TEST_F(MslGeneratorImplTest, EmitType_Struct_Layout_ArrayVec3DefaultStride) {
 TEST_F(MslGeneratorImplTest, AttemptTintPadSymbolCollision) {
     auto* s = Structure("S", utils::Vector{
                                  // uses symbols tint_pad_[0..9] and tint_pad_[20..35]
-                                 Member("tint_pad_2", ty.i32(), utils::Vector{MemberSize(32)}),
+                                 Member("tint_pad_2", ty.i32(), utils::Vector{MemberSize(32_a)}),
                                  Member("tint_pad_20", ty.f32(),
                                         utils::Vector{MemberAlign(128_u), MemberSize(128_u)}),
                                  Member("tint_pad_33", ty.vec2<f32>()),
diff --git a/src/tint/writer/wgsl/generator_impl.cc b/src/tint/writer/wgsl/generator_impl.cc
index b2fba295d3..83a96d9164 100644
--- a/src/tint/writer/wgsl/generator_impl.cc
+++ b/src/tint/writer/wgsl/generator_impl.cc
@@ -788,7 +788,11 @@ bool GeneratorImpl::EmitAttributes(std::ostream& out,
                 return true;
             },
             [&](const ast::StructMemberSizeAttribute* size) {
-                out << "size(" << size->size << ")";
+                out << "size(";
+                if (!EmitExpression(out, size->expr)) {
+                    return false;
+                }
+                out << ")";
                 return true;
             },
             [&](const ast::StructMemberAlignAttribute* align) {
diff --git a/src/tint/writer/wgsl/generator_impl_type_test.cc b/src/tint/writer/wgsl/generator_impl_type_test.cc
index ef90579c55..f6f39d4a2f 100644
--- a/src/tint/writer/wgsl/generator_impl_type_test.cc
+++ b/src/tint/writer/wgsl/generator_impl_type_test.cc
@@ -178,8 +178,8 @@ TEST_F(WgslGeneratorImplTest, EmitType_Struct) {
 
 TEST_F(WgslGeneratorImplTest, EmitType_StructOffsetDecl) {
     auto* s = Structure("S", utils::Vector{
-                                 Member("a", ty.i32(), utils::Vector{MemberOffset(8)}),
-                                 Member("b", ty.f32(), utils::Vector{MemberOffset(16)}),
+                                 Member("a", ty.i32(), utils::Vector{MemberOffset(8_a)}),
+                                 Member("b", ty.f32(), utils::Vector{MemberOffset(16_a)}),
                              });
 
     GeneratorImpl& gen = Build();
@@ -199,8 +199,8 @@ TEST_F(WgslGeneratorImplTest, EmitType_StructOffsetDecl) {
 TEST_F(WgslGeneratorImplTest, EmitType_StructOffsetDecl_WithSymbolCollisions) {
     auto* s =
         Structure("S", utils::Vector{
-                           Member("tint_0_padding", ty.i32(), utils::Vector{MemberOffset(8)}),
-                           Member("tint_2_padding", ty.f32(), utils::Vector{MemberOffset(16)}),
+                           Member("tint_0_padding", ty.i32(), utils::Vector{MemberOffset(8_a)}),
+                           Member("tint_2_padding", ty.f32(), utils::Vector{MemberOffset(16_a)}),
                        });
 
     GeneratorImpl& gen = Build();
@@ -237,8 +237,8 @@ TEST_F(WgslGeneratorImplTest, EmitType_StructAlignDecl) {
 
 TEST_F(WgslGeneratorImplTest, EmitType_StructSizeDecl) {
     auto* s = Structure("S", utils::Vector{
-                                 Member("a", ty.i32(), utils::Vector{MemberSize(16)}),
-                                 Member("b", ty.f32(), utils::Vector{MemberSize(32)}),
+                                 Member("a", ty.i32(), utils::Vector{MemberSize(16_a)}),
+                                 Member("b", ty.f32(), utils::Vector{MemberSize(32_a)}),
                              });
 
     GeneratorImpl& gen = Build();