Measuring Basement Windows

[mindless06795]

Hello,
I currently have old windows in my basement. They are the small, rectangular style. Encased by cement on three sides, and wood header on the top. I want to replace these with some Hopper style replacement windows. My question is, how do I measrue them? I can measure normal replacement windows no problem, but for these, I want to get the right and not sure where to measure from? Do the new one attach to the cement also? Thank you for any help.

[HayZee518]

the following thread pretty much address your problem.
Basement windows in Concrete - DoItYourself.com Community Forums