How to Measure Windows
Windows are measured and quoted by the united inch, what is a united inch you say?

United inch is the width plus the height, Example say the width of the window is 32 inches and the height of the window 54 inches if you add these together 32 plus 54 you would get a total of 86 united inches

Measure the windows from the inside of the trim of the interior window. 

If there is no window trim, measure from the inside of the plaster to plaster.

As long as your measurements are to the whole next inch, we can validate your quote.
Types of Windows
Double Hung
Bay Window
Casement
Bow Window
Picture Window
Patio Door
Awning Window
Garden Window
French Door
Slider Window
Geometric