diff -r 8f385b1fd0b6 src/video/windows/SDL_windowsvideo.c
--- a/src/video/windows/SDL_windowsvideo.c	Sun Dec 31 03:51:17 2017 -0500
+++ b/src/video/windows/SDL_windowsvideo.c	Sun Dec 31 19:36:46 2017 +0100
@@ -143,7 +143,10 @@
     device->SetWindowIcon = WIN_SetWindowIcon;
     device->SetWindowPosition = WIN_SetWindowPosition;
     device->SetWindowSize = WIN_SetWindowSize;
+    device->GetWindowBordersSize = WIN_GetWindowBordersSize;
     device->SetWindowOpacity = WIN_SetWindowOpacity;
     device->ShowWindow = WIN_ShowWindow;
     device->HideWindow = WIN_HideWindow;
     device->RaiseWindow = WIN_RaiseWindow;
diff -r 8f385b1fd0b6 src/video/windows/SDL_windowswindow.c
--- a/src/video/windows/SDL_windowswindow.c	Sun Dec 31 03:51:17 2017 -0500
+++ b/src/video/windows/SDL_windowswindow.c	Sun Dec 31 19:36:46 2017 +0100
@@ -479,6 +479,91 @@
     WIN_SetWindowPositionInternal(_this, window, SWP_NOCOPYBITS | SWP_NOMOVE | SWP_NOACTIVATE);
 }
 
+int
+WIN_GetWindowBordersSize(_THIS, SDL_Window * window, int *top, int *left, int *bottom, int *right)
+{
+    HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
+    RECT rcClient, rcWindow;
+    POINT ptDiff;
+
+    /* rcClient stores the size of the inner window, while rcWindow stores the outer size relative to the top-left
+     * screen position; so the top/left values of rcClient are always {0,0} and bottom/right are {height,width} */
+    GetClientRect(hwnd, &rcClient);
+    GetWindowRect(hwnd, &rcWindow);
+
+    /* convert the top/left values to make them relative to
+     * the window; they will end up being slightly negative */
+    ptDiff.y = rcWindow.top;
+    ptDiff.x = rcWindow.left;
+
+    ScreenToClient(hwnd, &ptDiff);
+
+    rcWindow.top  = ptDiff.y;
+    rcWindow.left = ptDiff.x;
+
+    /* convert the bottom/right values to make them relative to the window,
+     * these will be slightly bigger than the inner width/height */
+    ptDiff.y = rcWindow.bottom;
+    ptDiff.x = rcWindow.right;
+
+    ScreenToClient(hwnd, &ptDiff);
+
+    rcWindow.bottom = ptDiff.y;
+    rcWindow.right  = ptDiff.x;
+
+    /* Now that both the inner and outer rects use the same coordinate system we can substract them to get the border size.
+     * Keep in mind that the top/left coordinates of rcWindow are negative because the border lies slightly before {0,0},
+     * so switch them around because SDL2 wants them in positive. */
+    *top    = rcClient.top    - rcWindow.top;
+    *left   = rcClient.left   - rcWindow.left;
+    *bottom = rcWindow.bottom - rcClient.bottom;
+    *right  = rcWindow.right  - rcClient.right;
+
+    return 0;
+}
+
 void
 WIN_ShowWindow(_THIS, SDL_Window * window)
 {
diff -r 8f385b1fd0b6 src/video/windows/SDL_windowswindow.h
--- a/src/video/windows/SDL_windowswindow.h	Sun Dec 31 03:51:17 2017 -0500
+++ b/src/video/windows/SDL_windowswindow.h	Sun Dec 31 19:36:46 2017 +0100
@@ -58,7 +58,10 @@
 extern void WIN_SetWindowIcon(_THIS, SDL_Window * window, SDL_Surface * icon);
 extern void WIN_SetWindowPosition(_THIS, SDL_Window * window);
 extern void WIN_SetWindowSize(_THIS, SDL_Window * window);
+extern int WIN_GetWindowBordersSize(_THIS, SDL_Window * window, int *top, int *left, int *bottom, int *right);
 extern int WIN_SetWindowOpacity(_THIS, SDL_Window * window, float opacity);
 extern void WIN_ShowWindow(_THIS, SDL_Window * window);
 extern void WIN_HideWindow(_THIS, SDL_Window * window);
 extern void WIN_RaiseWindow(_THIS, SDL_Window * window);