diff --git a/vlib/v/ast/table.v b/vlib/v/ast/table.v
index 6bb60cbb39..79c5a95d3d 100644
--- a/vlib/v/ast/table.v
+++ b/vlib/v/ast/table.v
@@ -44,6 +44,7 @@ pub mut:
 	mdeprecated_msg   map[string]string    // module deprecation message
 	mdeprecated_after map[string]time.Time // module deprecation date
 	builtin_pub_fns   map[string]bool
+	pointer_size      int
 }
 
 // used by vls to avoid leaks
diff --git a/vlib/v/ast/type_size_test.v b/vlib/v/ast/type_size_test.v
new file mode 100644
index 0000000000..8e203aac4d
--- /dev/null
+++ b/vlib/v/ast/type_size_test.v
@@ -0,0 +1,54 @@
+import v.builder
+import v.parser
+import v.pref
+
+struct T01 {
+	a int
+	b byte
+	c int
+}
+
+type T02 = string
+type T03 = int | string
+type T04 = []T03
+type T05 = [47]T03
+
+interface T06 {
+	a int
+}
+
+interface T07 {
+	T06
+	b int
+}
+
+struct T08 {
+	T01
+	x string
+}
+
+fn test_type_size() ? {
+	mut pref := pref.new_preferences()
+	$if x64 {
+		pref.m64 = true
+	}
+	mut b := builder.new_builder(pref)
+	mut files := b.get_builtin_files()
+	b.set_module_lookup_paths()
+	parser.parse_files(files, b.table, b.pref)
+	b.parse_imports()
+	parser.parse_file(@FILE, b.table, .parse_comments, b.pref)
+
+	mut t := b.table
+
+	assert sizeof(T01) == t.type_size(t.type_idxs['main.T01'] ?)
+	assert sizeof(T02) == t.type_size(t.type_idxs['main.T02'] ?)
+	assert sizeof(T03) == t.type_size(t.type_idxs['main.T03'] ?)
+	assert sizeof(T04) == t.type_size(t.type_idxs['main.T04'] ?)
+	assert sizeof(T05) == t.type_size(t.type_idxs['main.T05'] ?)
+	assert sizeof(T06) == t.type_size(t.type_idxs['main.T06'] ?)
+	assert sizeof(T07) == t.type_size(t.type_idxs['main.T07'] ?)
+	assert sizeof(T08) == t.type_size(t.type_idxs['main.T08'] ?)
+
+	println('done')
+}
diff --git a/vlib/v/ast/types.v b/vlib/v/ast/types.v
index 2415b71aca..97935bafac 100644
--- a/vlib/v/ast/types.v
+++ b/vlib/v/ast/types.v
@@ -823,6 +823,97 @@ pub fn (t &TypeSymbol) is_builtin() bool {
 	return t.mod == 'builtin'
 }
 
+// type_size returns the size in bytes of `typ`, similarly to  C's `sizeof()`.
+pub fn (t &Table) type_size(typ Type) int {
+	if typ.has_flag(.optional) {
+		return t.type_size(ast.error_type_idx)
+	}
+	if typ.nr_muls() > 0 {
+		return t.pointer_size
+	}
+	sym := t.sym(typ)
+	match sym.kind {
+		.placeholder, .void, .none_ {
+			return 0
+		}
+		.voidptr, .byteptr, .charptr, .function, .usize, .isize, .any, .thread, .chan {
+			return t.pointer_size
+		}
+		.i8, .u8, .char, .bool {
+			return 1
+		}
+		.i16, .u16 {
+			return 2
+		}
+		.int, .u32, .rune, .f32, .enum_ {
+			return 4
+		}
+		.i64, .u64, .int_literal, .f64, .float_literal {
+			return 8
+		}
+		.alias {
+			return t.type_size((sym.info as Alias).parent_type)
+		}
+		.struct_, .string, .multi_return {
+			mut max_alignment := 0
+			mut total_size := 0
+			types := if sym.info is Struct {
+				sym.info.fields.map(it.typ)
+			} else {
+				(sym.info as MultiReturn).types
+			}
+			for ftyp in types {
+				field_size := t.type_size(ftyp)
+				alignment := if field_size > t.pointer_size { t.pointer_size } else { field_size }
+				if alignment > max_alignment {
+					max_alignment = alignment
+				}
+				total_size = round_up(total_size, alignment) + field_size
+			}
+			return round_up(total_size, max_alignment)
+		}
+		.sum_type, .interface_, .aggregate {
+			match sym.info {
+				SumType, Aggregate {
+					return (sym.info.fields.len + 2) * t.pointer_size
+				}
+				Interface {
+					mut res := (sym.info.fields.len + 2) * t.pointer_size
+					for etyp in sym.info.embeds {
+						res += t.type_size(etyp) - 2 * t.pointer_size
+					}
+					return res
+				}
+				else {
+					// unreachable
+					return 0
+				}
+			}
+		}
+		.array_fixed {
+			info := sym.info as ArrayFixed
+			return info.size * t.type_size(info.elem_type)
+		}
+		// TODO hardcoded:
+		.map {
+			return if t.pointer_size == 8 { 120 } else { 80 }
+		}
+		.array {
+			return if t.pointer_size == 8 { 32 } else { 24 }
+		}
+		.generic_inst {
+			return 0
+		}
+	}
+}
+
+// round_up rounds the number `n` up to the next multiple `multiple`.
+// Note: `multiple` must be a power of 2.
+[inline]
+fn round_up(n int, multiple int) int {
+	return (n + multiple - 1) & -multiple
+}
+
 // for debugging/errors only, perf is not an issue
 pub fn (k Kind) str() string {
 	return match k {
diff --git a/vlib/v/builder/builder.v b/vlib/v/builder/builder.v
index 266b0c8c5b..8750ebb39d 100644
--- a/vlib/v/builder/builder.v
+++ b/vlib/v/builder/builder.v
@@ -53,6 +53,7 @@ pub fn new_builder(pref &pref.Preferences) Builder {
 	if pref.use_color == .never {
 		util.emanager.set_support_color(false)
 	}
+	table.pointer_size = if pref.m64 { 8 } else { 4 }
 	msvc := find_msvc(pref.m64) or {
 		if pref.ccompiler == 'msvc' {
 			// verror('Cannot find MSVC on this OS')
diff --git a/vlib/v/checker/check_types.v b/vlib/v/checker/check_types.v
index c8ef5617df..6c846a1db0 100644
--- a/vlib/v/checker/check_types.v
+++ b/vlib/v/checker/check_types.v
@@ -709,38 +709,3 @@ pub fn (mut c Checker) infer_fn_generic_types(func ast.Fn, mut node ast.CallExpr
 		c.need_recheck_generic_fns = true
 	}
 }
-
-pub fn (c &Checker) sizeof_integer(a ast.Type) int {
-	t := if a in ast.unsigned_integer_type_idxs { a.flip_signedness() } else { a }
-	r := match t {
-		ast.char_type_idx, ast.i8_type_idx {
-			1
-		}
-		ast.i16_type_idx {
-			2
-		}
-		ast.int_type_idx {
-			4
-		}
-		ast.rune_type_idx {
-			4
-		}
-		ast.i64_type_idx {
-			8
-		}
-		ast.isize_type_idx {
-			if c.pref.m64 { 8 } else { 4 }
-		}
-		ast.int_literal_type {
-			s := c.table.type_to_str(a)
-			panic('`$s` has unknown size')
-			0
-		}
-		else {
-			s := c.table.type_to_str(a)
-			panic('`$s` is not an integer')
-			0
-		}
-	}
-	return r
-}
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 0fff2cad46..9f3f15ddb9 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -643,8 +643,8 @@ pub fn (mut c Checker) infix_expr(mut node ast.InfixExpr) ast.Type {
 				} else if is_left_type_signed != is_right_type_signed
 					&& left_type != ast.int_literal_type_idx
 					&& right_type != ast.int_literal_type_idx {
-					ls := c.sizeof_integer(left_type)
-					rs := c.sizeof_integer(right_type)
+					ls := c.table.type_size(left_type)
+					rs := c.table.type_size(right_type)
 					// prevent e.g. `u32 == i16` but not `u16 == i32` as max_u16 fits in i32
 					// TODO u32 == i32, change < to <=
 					if (is_left_type_signed && ls < rs) || (is_right_type_signed && rs < ls) {
diff --git a/vlib/v/checker/comptime.v b/vlib/v/checker/comptime.v
index 440de78324..62d78fa41e 100644
--- a/vlib/v/checker/comptime.v
+++ b/vlib/v/checker/comptime.v
@@ -127,30 +127,7 @@ fn (mut c Checker) eval_comptime_const_expr(expr ast.Expr, nlevel int) ?ast.Comp
 		//	return expr.val.i64()
 		// }
 		ast.SizeOf {
-			xtype := expr.typ
-			if xtype.is_real_pointer() {
-				if c.pref.m64 {
-					return 8 // 64bit platform
-				}
-				return 4 // 32bit platform
-			}
-			if int(xtype) == xtype.idx() {
-				match xtype {
-					ast.char_type { return 1 }
-					ast.i8_type { return 1 }
-					ast.i16_type { return 2 }
-					ast.int_type { return 4 }
-					ast.i64_type { return 8 }
-					//
-					ast.byte_type { return 1 }
-					// ast.u8_type { return 1 }
-					ast.u16_type { return 2 }
-					ast.u32_type { return 4 }
-					ast.u64_type { return 8 }
-					else {}
-				}
-			}
-			return none
+			return c.table.type_size(expr.typ)
 		}
 		ast.FloatLiteral {
 			x := expr.val.f64()