Today I made a small calculator for cutting mat-boards.
It is small, fast, and versatile.
It might meet all your matting needs.
The program is free!
I programed it in C++, for 32-bit windows.
It runs fine on 64-bit or 32-bit, Win-7.
It should run in Vista, Win-XP, Win-7, and Win-8.
Link to page with screen-grabs and more info.