Usually your windows are installed into a wood frame or rough stud opening (RSO). Sometimes they are brick to brick.
Either way measure from inside frame to inside frame to determine the height and width.
NOTE: For replacement windows deduct 1/4 inch from both height and width. For new home construction or if putting the windows into new wooden frames deduct 1/2 inch as per building codes.

For pricing we have:
Please remember all styles have minimum sizes. Please keep minimums in mind when calculating prices.
Now that we have our measurements, lets go to Styles and Prices.