How to measure up for a new door

Replacing an internal or external door? You’ll need to measure the existing door frame to get the best fit. Even if you’re 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 we offer many different widths, thicknesses and sizes to ensure the best fit and the best finish.

There are a few basic rules to remember first:

  • Take the measurement from 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, 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

It’s important to note 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.

Would you like to empty your basket?

Yes No


It seems you are running an older version of Internet Explorer. Our site does not support these old browsers as they do not house the technology that allows our site to be safe and secure.

If you wish to access our site please either upgrade your browser or download an alternative.