NMutch

I'm missing something and I'm sure it's simple. In chief when I dimension a window it seems to dimension the glass. I am a supplier as well and when I build a window in my window manufacturers software it references the outside of the frame as well as tip to tip and rough openings required. Is there a way to build a 24" x 24" window that means 24" is outside of frame requiring a 25 1/4" Rough opening? Thanks in advance.