diff --git a/source/Platform/Win32/Win32Display.cpp b/source/Platform/Win32/Win32Display.cpp
index 7e89676..eeecffe 100644
--- a/source/Platform/Win32/Win32Display.cpp
+++ b/source/Platform/Win32/Win32Display.cpp
@@ -284,6 +284,13 @@ Vector2i Win32Display::centerWindow(int width, int height)
 	return v;
 }
 
+Vector2u Win32Display::calculateSize(DWORD flags, LONG width, LONG height)
+{
+	RECT r = {0, 0, width, height};
+	AdjustWindowRect(&r, flags, false);
+	return Vector2u(r.right - r.left, r.bottom - r.top);
+}
+
 void Win32Display::enterFullscreen(DisplayMode mode)
 {
 	LONG rc;
diff --git a/source/Platform/Win32/Win32Display.h b/source/Platform/Win32/Win32Display.h
index 510c275..5d7b4fe 100644
--- a/source/Platform/Win32/Win32Display.h
+++ b/source/Platform/Win32/Win32Display.h
@@ -55,6 +55,8 @@ protected :
 
 	void registerClass();
 
+	Vector2u calculateSize(DWORD flags, LONG width, LONG height);
+
 	DWORD getWin32Flags(unsigned int flags);
 
 	Vector2i centerWindow(int width, int height);