Measure the width, height, and depth in 3 places. For width, use the smallest measurement to the nearest 1/8". For height, use the longest measurement to the nearest 1/8”
For inside mounts, we will take any necessary deductions for clearance
For outside mounts, consider adding overlapping width and height to ensure the entire window is covered
Use a steel tape measure for accuracy
Measure all windows, even those that appear to be the same width and height