How do you measure patio doors?

Patio doors should be measured from the inside surface of the studs surrounding the doors. Both horizontal and vertical measurements are necessary, covering the top and bottom of the doors as well as both sides. After getting the measurements, use the shortest horizontal and vertical measurements for sizing.

To access the studs surrounding the doors, the patio door casing on the edges must be removed. Removal instructions are usually found in the installation instructions for the doors that were provided by the manufacturer. Once removed, the casing is generally saved for use if the existing patio doors are being replaced.