Replacing an internal or external door? You’ll need to measure the existing door frame to get the best fit. Even if you were confident in the size of your door when you bought it, it may have needed to be trimmed before it fit completely so it’s best to double-check. The average width of an internal door is 762mm, but here at Door Superstore we offer many different widths, thicknesses and sizes to ensure the best fit and the best finish.

Read on to find out how to measure a door.

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There are a few basic rules to remember first:

  • Measure from the inside of the door frame, not the door itself
  • Take measurements in millimetres (feet and inches are a thing of the past)
  • It’s always better to buy bigger than smaller

How to measure a door:

  1. Measure the width inside the door frame at the top, in the middle, and at the bottom – the widest measurement is the one you want to buy, and the narrower parts can be trimmed or sanded down for a good fit
  2. Measure the height from inside the door frame, from the floor to the top – do this once on the left side and once on the right side. Use the longest length as the height measurement (don’t forget to account for any flooring that isn’t laid yet)
  3. Use your widest width and tallest height measurements to select your door
  4. If your measurements are unavailable then buy the next size up, as the door can be sanded and played with to get the correct fit

Bear in mind that it’s still important to measure and select the closest door size. Most doors can only be trimmed by a few mm and many fire doors cannot be trimmed at all.

For further advice about measuring for new doors or doors in general, contact our support team using the live chat or give us a call on 01752 422 501.


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