Step1
Measure the Width
Measure the window recess width at three points, use the smallest measurement, and subtract 5mm.
This is your width measurement.
Step2
Measure the Drop
Measure from the bottom of the opening to the center or, for sash windows, to the break point. Then, deduct 2.5mm.
This is your drop measurement.
Step3
Enter your Measurements
Go to your chosen product, enter your width and drop measurements.