diff --git a/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.h b/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.h
index fa9a38919f..52278f2d38 100644
--- a/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.h
+++ b/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.h
@@ -21,6 +21,8 @@ public:
 	void *GetProcAddress( RString s );
 	RString TryVideoMode( const VideoModeParams& p, bool& newDeviceOut );	
 	void GetDisplayResolutions( DisplayResolutions &dr ) const;
+	float GetMonitorAspectRatio() const;
+
 	void SwapBuffers();
 	void Update();
 	
diff --git a/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.mm b/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.mm
index 11e811915b..183c5ac11b 100644
--- a/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.mm
+++ b/stepmania/src/arch/LowLevelWindow/LowLevelWindow_Cocoa.mm
@@ -411,6 +411,11 @@ void LowLevelWindow_Cocoa::GetDisplayResolutions( DisplayResolutions &dr ) const
 	// Do not release modes! We don't own it here.
 }
 
+float LowLevelWindow_Cocoa::GetMonitorAspectRatio() const
+{
+	return 4/3.f;
+}
+
 void LowLevelWindow_Cocoa::SwapBuffers()
 {
 	CGLFlushDrawable( CGLGetCurrentContext() );
diff --git a/stepmania/src/archutils/Win32/GraphicsWindow.cpp b/stepmania/src/archutils/Win32/GraphicsWindow.cpp
index 0207be7b32..9ea1f893a6 100644
--- a/stepmania/src/archutils/Win32/GraphicsWindow.cpp
+++ b/stepmania/src/archutils/Win32/GraphicsWindow.cpp
@@ -516,6 +516,18 @@ void GraphicsWindow::GetDisplayResolutions( DisplayResolutions &out )
 	}
 }
 
+float GraphicsWindow::GetMonitorAspectRatio()
+{
+	// There's no way to query the monitor for this, so assume that the
+	// normal desktop resolution is using square pixels.
+	DEVMODE dm;
+	ZERO( dm );
+	dm.dmSize = sizeof(dm);
+	BOOL bResult = EnumDisplaySettings( NULL, ENUM_REGISTRY_SETTINGS, &dm );
+	ASSERT( bResult );
+	return dm.dmPelsWidth / (float)dm.dmPelsHeight;
+}
+
 
 /*
  * (c) 2004 Glenn Maynard
diff --git a/stepmania/src/archutils/Win32/GraphicsWindow.h b/stepmania/src/archutils/Win32/GraphicsWindow.h
index 62a921bee2..bb305178b0 100644
--- a/stepmania/src/archutils/Win32/GraphicsWindow.h
+++ b/stepmania/src/archutils/Win32/GraphicsWindow.h
@@ -6,6 +6,7 @@
 #include <windows.h>
 class VideoModeParams;
 class DisplayResolutions;
+class DisplayResolution;
 
 namespace GraphicsWindow
 {
@@ -20,6 +21,7 @@ namespace GraphicsWindow
 	void DestroyGraphicsWindow();
 
 	void GetDisplayResolutions( DisplayResolutions &out );
+	float GetMonitorAspectRatio();
 
 	const VideoModeParams &GetParams();
 	HDC GetHDC();