I want to change out an replacement window installed 10 years ago. What's procedure to follow,to get new window with correct measurements????? Thanks :)

It will vary upon windows, but in general you measure from jamb to jamb make sure you not measureing from the window stop, and from the top jamb down to where the sash hits at the bottom.

it will vary upon windows, but in general you measure from jamb to jamb make sure you not measureing from the window stop, and from the top jamb down to where the sash hits at the bottom.

Yes measure from Jamb to Jamb, but subtract a 1/2" that seems to always help so that you don't get a window to tight, and also allows for adjustable main frame screw to operate.