To ensure the correct measurement of windows, measure your windows by width first. Measure first at the top, then the middle and finally the bottom. Be sure to measure from the surface of the jambs, and not from the trim strips. Use the smallest of these three measurements when ordering your window.
After measuring the width, measure the height in a similar fashion, starting with the top, then the middle and then the bottom. Again use the smallest measurement of the three. Remember, though, costly mistakes can happen if you are even off by a few centimeters.
When replacing your windows it is always a good idea to use a professional you can trust. DenCo in Denver, Colorado will gladly give you an assessment of what type of window will work best for you, and provide you with a quote that is both fair and affordable.