How to Measure a Door Opening for a Replacement Door

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To measure a door opening for a replacement, take the width at the top, middle and bottom, the height at the left, middle and right, and the depth of the wall opening. Use the smallest measurement in each direction, and record whether the door swings in or out and which side the hinges are on.

Why accurate measurements matter

A replacement door is usually made to measure, so the numbers you send must match the opening exactly. Walls are rarely perfectly straight, and an older opening can be out of square by a few millimeters or more. Taking measurements carefully saves time, avoids a door that does not fit, and reduces the need for adjustments during installation.

Before you start, clear the area, have a steel tape measure and a pencil ready, and ideally work with a second person to hold the tape straight.

Measure the width

Measure the width of the opening from one side of the frame to the other, between the inner faces of the jambs. Take three readings: at the top, in the middle and at the bottom. Walls can narrow or widen slightly, so use the smallest of the three as your reference width.

If the door will sit on top of an existing frame, measure the frame itself rather than the wall plaster, and note whether the frame will be removed.

Measure the height

Measure the height from the finished floor up to the underside of the lintel or the top of the frame. Take readings on the left, in the middle and on the right. Use the shortest result. If the floor is not finished yet, note that, because the final floor level will change the usable height.

Also check whether there is a threshold or step, since it affects how the bottom of the door will sit.

Check the depth and wall thickness

Measure the depth of the opening, which is the thickness of the wall where the frame will sit. This tells the manufacturer how the frame must be built and whether it fits into the opening without gaps. For steel and aluminum doors, depth is especially important when the door is installed into a masonry or concrete wall.

Note any recesses, plaster returns or protruding tiles that could reduce the usable depth.

Note the swing, hinge side and opening direction

Decide how the door should open: inward or outward, and whether it should swing to the left or right. Stand outside the room facing the door and mark the hinge side. This information is needed to produce hinges, locks and handles in the correct position.

Inward or outward opening
Left or right hinge side
Position of any handle and lock

Prepare your measurement sheet

Write all measurements on one sheet, labeled clearly: width (top, middle, bottom), height (left, middle, right), depth, swing direction, hinge side, and whether the door is for inside or outside. Add a few photos of the opening from the front and the side, with a tape measure visible in the frame.

A clear sheet and photos make it easier for the factory to confirm the order and reduce back-and-forth questions.

Frequently asked questions

Should I measure the rough opening or the finished opening?

Measure the finished opening, meaning the space between the wall finishes where the frame will sit. If plaster or tiling is still to be done, note that and measure again after the work is complete.

What if the walls are not straight?

Take several readings and use the smallest width and height. Noting the variation on your sheet helps the manufacturer plan the frame and fitting.

Do I need to remove the old door before measuring?

It is not always necessary, but removing the old door gives you better access to the frame and wall. If you do remove it, take photos of the hinges and frame first.

Can I send measurements by WhatsApp?

Yes, you can send your measurements and photos by WhatsApp. An on-site measurement may still be recommended for a precise fit.

Common mistakes to avoid

The most common mistakes are measuring only once, using a single reading instead of several, and forgetting to note the swing direction. Always take multiple readings and record the hinge side before you order.

Our recommendation

Measure at least three points for width and height, use the smallest values, and send photos with the sheet. If the opening is old or irregular, ask for an on-site measurement before production.

Summary

Measure the width, height and depth at several points, note the swing and hinge side, and record everything with photos before ordering a replacement door.

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