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How to determine the Measurements of a Front Door

Anyone that is considering installing new front doors needs to measure first. A smooth installation procedure can be guaranteed only if the measurements of the front door and the surrounding masonry are measured correctly. However, there are several things to bear in mind when calculating the required dimensions. If you want to determine the size of the door, just follow this step-by-step manual for do-it-yourself enthusiasts. Here, you will learn which tools you will need and how the various steps are carried out most efficiently.


  • Tape measure

1. Preparations

Before taking the measurements necessary for installing front doors, you should use the pen and paper to create a rough sketch your current door. Once measured, you can conveniently note the measured height and width of the reveal, which will give you the precise dimensions required when ordering your new door. Do not forget to mark the location of the door handle as well.

Although the dimensions of the reveal may be found in the blueprints of the building, these measurements are often no longer not up-to-date. Particularly in older buildings, this may be the case after years of renovations. The data recorded when re-measuring the reveal should not only be used during the ordering process but you should also write down the most recent figures onto the original blueprints. This saves you time should you renovate your home in the future. This is why the measurements should always be listed with their date (Fig. 1).

If you have measured the width and height correctly, you can use these measurements again. The dimensions of the reveal can also serve to simplify the installation of a mosquito screen as there will be no need for re-measuring.

2. Measuring Front Doors in Old Buildings

To determine the necessary dimensions of your new front door, you need to measure the dimensions of the frame of an already installed door. Due to technical and architectural reasons, the dimensions in older buildings can be very different from those in newer buildings. Please only follow the steps below if you are taking measurements in an older building:

Regardless of whether you want to measure front doors, interior doors or even special models such as fire doors – measurements are always taken from a perspective of looking out from the inside of the building. Furthermore, the dimensions of the frame are usually given in millimetres.

a) Measuring the Height

    • First, you should measure the height of the frame at its innermost point. Measure twice, from the floor to the upper edge on both the right and left side of the front door. To ensure the smooth installation of an aluminium or wooden front door you should use the smaller of the two measured values and deduct 10 mm. This gap is necessary, as sealing materials will need to be applied at a later time.
    • Afterwards you should also determine the height of the frame, measuring from its lower outer edge to its upper outer edge. This should once again be done both on the left and right-hand sides. Determine the height of the frame and deduct 10 mm.
    • Usually, the required height of any front door is determined by measuring along the innermost edges in the way described above. However, if you notice a frame height difference between the inner and outer thresholds of the lower section of the front door, the installation will be slightly more difficult. In such a case, you will need to follow detailed instructions for determining the correct height. In such cases, you can use these detailed drawing.

    For example: If the measured height is greater on the inside than on the outside, then we usually suggest installing the threshold further outward; the height difference to the inner section should then be bridged with a cover strip.

    b) Measuring the Width

    • Now, you should measure the door in order to determine the required width of a new front door. You will need to determine the width of the rebate – the distance between the left and right sides of the reveal – first. Once again, you should take two measurements, measuring the width both on the upper and the lower parts of the reveal.
    • Now deduct 20 millimetres from the smaller result to ensure that the front door can properly fit into the reveal.

    For example: At a width of 1240 mm in the upper section and 1230 mm in the lower section, you need to deduct 10 mm from the smaller result. This will leave you with an ideal width of 1210 mm.

    3. Measuring Front Doors in New Buildings

    Determining frame height and width in newly constructed buildings is significantly easier. In a new building you will only need the clear distance to calculate the dimension for the front door. The overall frame size is simply the open space between the openings in a wall.

    a) Measuring the Height

        • Measuring the required height for doors in new buildings is easily done by determining the vertical measurements of the opening in the wall – the distance from the lower part of the reveal to the top. To make sure you take the right measurements, you should once again measure twice, at the left-hand and right-hand sides respectively.
        • Now use the smaller value as a base, and determine the required height of your new door by deducting 20 mm.
        • The floor also has to be taken into account when measuring the required height. The height of the flooring determines whether an extension of the frame is necessary. Simply determine the height of the flooring and deduct 10 millimetres. The resulting value determines the size of the necessary frame extension for the front door. Please refer to our measuring guide if you have any questions.

            For example: The height of the wall opening is 2200 mm. This means that the required height of your door should be 2180 mm. If your flooring has a height of 150 mm, the size of the frame extension should be 140 mm. This is necessary so that the floor and the threshold are flush.

            b) Measuring the Width

            • In order to measure the width of the front door correctly, you should take the measurements of the distance between the left and right-hand sides of the reveal from two separate points (upper and lower sections).
            • Again, subtract 20 millimetres from the smaller value to determine the necessary dimensions for your new door.

            For example: You have measured a width of 1260 mm. The correct width of the door that you need to order is therefore 1240 mm.

            Using this manual, you can now easily determine the required height and width of your new wooden or aluminium front door. You have also learned all the necessary steps for determining the correct dimensions of interior and fire doors. Measurements of those types of doors can be taken in a very similar fashion. Thus, this manual can help you prepare for the respective procedures optimally.

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