Just make sure the window you are looking at is certified egress window (there should be a stick for the inspector) and any good manufacturer will have necessary back-up.
It is more than just the square inchs since there are requirements for minimum height and width of the CLEAR opening. The other issue you have to face is an installation criteria. - It is the height from the bottom of the opening to the finished floor that can vary from locality to locality. Very costly to correct if it does not comply.