**VIM computes the width and height of its display area using columns and lines, not pixels**. Resize your GVIM window using your mouse, and you will notice the change.

Let's say the titlebar's height is 40px; when maximized, the width and height of GVIM window is 1024 X 722. Then, the total display area of VIM SHOULD be 1024 X 682 (722 - 40).

If the height of each line is 20px and each character (column) takes 5px, then there will be 51 (1024 / 20) lines and 4 (1024 mod 20) pixels, 136 (682 / 5) columns and 2 (682 mod 5) pixels.

**The actual width and height of VIM's display area is 1020 X 720 while the resolution of the GVIM window is 1024 X 722, this making the rest area unused (the gray area).**

How to fix it?

Never maximize the GVIM window, or you can use this trick:

```
:set lines=8888
:set columns=8888
```