diff --git a/lib/os.js b/lib/os.js
index 4426612285e299..f412a74132e4e3 100644
--- a/lib/os.js
+++ b/lib/os.js
@@ -54,3 +54,6 @@ if (binding.isBigEndian)
   exports.endianness = function() { return 'BE'; };
 else
   exports.endianness = function() { return 'LE'; };
+
+exports.sizeof = process.binding('sizeof').sizeof;
+exports.alignof = process.binding('sizeof').alignof;
diff --git a/node.gyp b/node.gyp
index 70c9841a89a176..11f669d8c3dcae 100644
--- a/node.gyp
+++ b/node.gyp
@@ -120,6 +120,7 @@
         'src/node_i18n.cc',
         'src/pipe_wrap.cc',
         'src/signal_wrap.cc',
+        'src/sizeof.cc',
         'src/smalloc.cc',
         'src/spawn_sync.cc',
         'src/string_bytes.cc',
diff --git a/src/sizeof.cc b/src/sizeof.cc
new file mode 100644
index 00000000000000..ebd78041c6c3ab
--- /dev/null
+++ b/src/sizeof.cc
@@ -0,0 +1,82 @@
+
+#include "env.h"
+#include "env-inl.h"
+#include "node.h"
+#include "node_internals.h"
+#include "v8-profiler.h"
+#include "v8.h"
+
+namespace node {
+namespace _sizeof {
+
+using v8::Context;
+using v8::Handle;
+using v8::Object;
+using v8::Uint32;
+using v8::Value;
+
+
+void Initialize(Handle<Object> exports,
+                Handle<Value> unused,
+                Handle<Context> context) {
+  Environment* env = Environment::GetCurrent(context);
+
+  Handle<Object> sizeof_obj = Object::New(env->isolate());
+  Handle<Object> alignof_obj = Object::New(env->isolate());
+
+#define SET_SIZEOF(name, type) \
+  sizeof_obj->Set(FIXED_ONE_BYTE_STRING(env->isolate(), #name), \
+               Uint32::NewFromUnsigned(env->isolate(), \
+                                       static_cast<uint32_t>(sizeof(type))));
+
+#define SET_ALIGNOF(name, type) \
+  alignof_obj->Set(FIXED_ONE_BYTE_STRING(env->isolate(), #name), \
+               Uint32::NewFromUnsigned(env->isolate(), \
+                                       static_cast<uint32_t>(alignof(type))));
+
+#define SET_TYPE(name, type) \
+  SET_SIZEOF(name, type) \
+  SET_ALIGNOF(name, type)
+
+  // fixed sizes
+  SET_TYPE(int8, int8_t);
+  SET_TYPE(uint8, uint8_t);
+  SET_TYPE(int16, int16_t);
+  SET_TYPE(uint16, uint16_t);
+  SET_TYPE(int32, int32_t);
+  SET_TYPE(uint32, uint32_t);
+  SET_TYPE(int64, int64_t);
+  SET_TYPE(uint64, uint64_t);
+  SET_TYPE(float, float);
+  SET_TYPE(double, double);
+
+  // (potentially) variable sizes
+  SET_TYPE(bool, bool);
+  SET_TYPE(byte, unsigned char);
+  SET_TYPE(char, char);
+  SET_TYPE(uchar, unsigned char);
+  SET_TYPE(short, short);
+  SET_TYPE(ushort, unsigned short);
+  SET_TYPE(int, int);
+  SET_TYPE(uint, unsigned int);
+  SET_TYPE(long, long);
+  SET_TYPE(ulong, unsigned long);
+  SET_TYPE(longlong, long long);
+  SET_TYPE(ulonglong, unsigned long long);
+  SET_TYPE(longdouble, long double);
+  SET_TYPE(pointer, char*);
+  SET_TYPE(size_t, size_t);
+
+#undef SET_SIZEOF
+#undef SET_ALIGNOF
+#undef SET_TYPE
+
+  exports->Set(FIXED_ONE_BYTE_STRING(env->isolate(), "sizeof"), sizeof_obj);
+  exports->Set(FIXED_ONE_BYTE_STRING(env->isolate(), "alignof"), alignof_obj);
+}
+
+
+}  // namespace _sizeof
+}  // namespace node
+
+NODE_MODULE_CONTEXT_AWARE_BUILTIN(sizeof, node::_sizeof::Initialize)