diff --git a/redo/container_windows.c b/redo/container_windows.c
index 5f71fe2..e393861 100644
--- a/redo/container_windows.c
+++ b/redo/container_windows.c
@@ -88,6 +88,7 @@ void calculateBaseUnits(HWND hwnd, int *baseX, int *baseY, LONG *internalLeading
 	HDC dc;
 	HFONT prevFont;
 	TEXTMETRICW tm;
+	SIZE size;
 
 	dc = GetDC(hwnd);
 	if (dc == NULL)
@@ -97,7 +98,9 @@ void calculateBaseUnits(HWND hwnd, int *baseX, int *baseY, LONG *internalLeading
 		xpanic("error loading control font into device context for preferred size calculation", GetLastError());
 	if (GetTextMetricsW(dc, &tm) == 0)
 		xpanic("error getting text metrics for preferred size calculations", GetLastError());
-	*baseX = (int) tm.tmAveCharWidth;		/* TODO not optimal; third reference below has better way */
+	if (GetTextExtentPoint32W(dc, L"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", 52, &size) == 0)
+		xpanic("error getting text extent point for preferred size calculations", GetLastError());
+	*baseX = (int) ((size.cx / 26 + 1) / 2);
 	*baseY = (int) tm.tmHeight;
 	*internalLeading = tm.tmInternalLeading;
 	if (SelectObject(dc, prevFont) != controlFont)
diff --git a/redo/container_windows.go b/redo/container_windows.go
index 41d7aad..5cd1877 100644
--- a/redo/container_windows.go
+++ b/redo/container_windows.go
@@ -86,6 +86,7 @@ func containerResize(data unsafe.Pointer, r *C.RECT) {
 // - http://msdn.microsoft.com/en-us/library/ms645502%28VS.85%29.aspx - the calculation needed
 // - http://support.microsoft.com/kb/125681 - to get the base X and Y
 // (thanks to http://stackoverflow.com/questions/58620/default-button-size)
+// In my tests (see https://github.com/andlabs/windlgunits), the GetTextExtentPoint32() option for getting the base X produces much more accurate results than the tmAveCharWidth option when tested against the sample values given in http://msdn.microsoft.com/en-us/library/windows/desktop/dn742486.aspx#sizingandspacing, but can be off by a pixel in either direction (probably due to rounding errors).
 
 // note on MulDiv():
 // div will not be 0 in the usages below