How to Determine the Measurements of a French Door

Determining the correct measurements for new construction components is a fundamental procedure for any renovation in the house. New doors and windows should only be ordered with correct dimensions. Anyone looking for a French door must therefore determine the correct measurements first. has developed this detailed manual, demonstrating all steps to determine the right dimensions for your French door.

1. Preparation

Determining the correct measurements is especially important, when windows in an old building need to be replaced.

Existing blueprints can be very helpful, but the given data may not be up to date, requiring all dimensions to be re-measured.

If differing measurements are detected, you need to write them down and note the date of change.

This saves time for renovations at a later date and can help avoid problems during the installation.

In order to help you with this, you can print this document and use it for your notes.

It makes no difference, whether the door is made of wood, aluminium or uPVC. (Fig. 1)

After all necessary measurements are written down correctly - whether French or front door - the data can later also be used for the installation of roller shutters and/or insect protection.

2. Measuring the Dimension of French Doors in old Buildings

Tip: Do also measure the dimensions outside. If the exterior figures are bigger than those inside, the door has to be installed from the outside. In this case you need to determine all necessary measurements outside as well.

  • Draw a sketch of the respective component. You can use it to fill in the measured values later. The opening direction of the French door as well as its handle should also be included in the sketch.
  • First, measure the inside width from the lower and upper sections of the doorframe. If the figures from the lower and upper sections differ, you should use the smaller one as the initial value. You have to deduct 20 mm from the initial value to ensure that there is still enough space allowing for the door to be attached to the masonry afterwards.
  • Now you need to determine the height of the French door with the same procedure and deduct 10 millimetres from the smaller value.

Example: Your measured height is 132.0 cm. Deduct 10 mm from this value and the measurement will be 131.0 cm. The width had the dimension 124.0 cm in the upper section and 123.0 in the lower. Deduct 20 mm from the smaller value. The final width is 121.0 cm.

3. Measuring the Dimensions of French Doors in new Buildings

With new buildings, the fact that there are no doors or windows installed makes it easier to determine the measurements for the installation of a French door.

  • First, the height of the door reveal (the wall opening) needs to be measured, deducting 20 millimetres afterwards. Although the measurements in these buildings should be very precise, it is more secure to re-measure them. Measure the height on the left and right hand side and also use the smaller value as basis.
  • The width can be determined by measuring the reveal width and deducting 20 mm from it.

Example: The determined values are 126.0 cm (width) and 146.0 cm (height). Deducting 20 mm from each value, the final sizes are 1240 mm (width) and 1440 mm (height).

Do you have further questions? also offers a detailed video manual concerning the measurements of French doors in a new building. 

Determining correct measurements is very important for the smooth installation of a French door without complications. This manual will help you to identify the necessary measurements for any type of door. Additionally, you will have learned the important steps for measuring uPVC, aluminium or wooden windows as well. Determining the measurements for these various window types is almost identical.

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