How To Measure For Your NEW External Door. - Daves Doors

Found an external door you like but not sure what size you need? This is where we can help!

Last updated: Jan 2026 — written by DavesDoors technical team (trade + installation experience since 2008). Learn how to measure for a new front door.

OK, so you have made the decision to purchase a new front door. You have determined the sort of door you currently have ( uPVC, Timber or Composite ) , you have had a quick google to see what is available ( from cheap, insecure uPVC, traditional timber panel or a rolls royce Composite door! ) and you have settled on a style/supplier….. (Obviously we appreciate there are other suppliers out there, and some of which are almost as good as Daves Doors!) Time to measure for your new front door.

Quick overview before you start: You should always measure the opening the door fits into — not the existing door itself. Take measurements in multiple places, use the largest width and height, and note whether you are replacing the door only or the door and frame, as this changes how you measure.

Not all suppliers offer a site survey service and even less offer this for free (our site surveys are free, but only available in our local installation area) so it is useful to be able to measure for your new front door yourself.

First things first, you will need a tape measure. This may sound obvious but we have had customers in the past trying to measure for their new door with a 30cm school ruler! This is obviously, wildly inaccurate, and also brings us onto the second point…

Units of measurement. As we all know, we currently have two units of measurement, imperial and metric. Although moving away from the imperial measuring system within the building trade, doors are often still referred to using imperial language, for example, a ‘normal’ external door tends to be 6’6 x 2’9 (six foot six inches by two foot nine inches) as this is still a ‘standard’ size for an external door. However this will often be show in both measurements like so…

1981 x 838 (6’6 x 2’9)

In metric, within the building and furniture trade, Centimetres (cm) are not a recognised unit of measurement due to their inaccuracy. Metric measurements are always portrayed in Millimetres (mm) as above.

Standard UK External Door Sizes

The three most common external door sizes measure as follows;

1981 x 762 (6’6 x 2’6)

1981 x 838 (6’6 x 2’9)

2032 x 813 (6’8 x 2’8)

Other sizes are available but these tend to be the most common.

Standard UK Front Door Sizes (Quick Reference)

Important: The sizes above are the door leaf (the door itself) — not the frame. If you are measuring an existing timber frame opening, you normally choose the nearest suitable leaf size and allow for fitting clearance during installation.

Common UK size (mm)	Common imperial name	Typical use
1981 x 762	6’6 x 2’6	Narrower openings / older properties
1981 x 838	6’6 x 2’9	Most common “standard” UK front door
2032 x 813	6’8 x 2’8	Often used on newer builds / slightly taller doors

If your opening is “between sizes”: with timber doors it’s usually safer to choose a door that’s slightly larger and have it trimmed/planed to fit. If you are replacing the door and frame, you may instead choose a smaller set and pack out the opening depending on site conditions.

OK, so far so good, right!?.....

The above sizes are based around an old industry standard wooden door opening. These measurements are the available sizes of wooden doors, NOT including the frame. For now we are only interested in measuring for a replacement wooden door, the technique for measuring for a new frame (or uPVC or Composite door which often come with the frame included) is very similar and we will get to that shortly…

When measuring for your new replacement front door, you must always measure your frame opening (that the door closes in to), NOT the existing door. Amongst other reasons, you are looking to replace the old door, normally due to a poor fit, rot or damage, so why would you want the new door to fit just as badly as the old one? The existing frame size is not going to change and is more likely to correlate to the list of door sizes available, making your choice a lot easier. (A timber door will almost always need to be cut down (fitted) to suit the frame opening. Better it be too big and cut down to fit, as opposed to just too small!)

Measuring for a new front door. (Wooden and Timber Doors).

Open your existing door towards you. You are going to measure the ‘hole’ within which the door was just sitting.

We recommend taking three measurements in the width (top, middle and bottom) and two measurements in the height (left and right)

These sizes are likely to vary, however try to favour the larger size as you can always cut some off your new front door, it’s a lot more difficult to stick some on!

Common measuring mistakes to avoid

• Measuring the old door instead of the frame opening

• Only taking one measurement instead of checking top, middle and bottom

• Measuring from raised internal flooring (tiles or laminate) instead of the structural opening

• Forgetting to allow fitting clearance

• Assuming the frame is square when it isn’t

Avoiding these mistakes now can save delays, extra costs, or ordering the wrong size door.

Measuring an external doors brickwork opening. (Replacement Timber door including frame OR Composite Doors)

Measuring your width is reasonably straight forward in this situation. An existing frame is usually set back slightly so taking an accurate ‘brick to brick’ measurement shouldn’t be an issue.

When measuring brick-to-brick, accuracy is especially important as this measurement determines the overall frame size. Always measure from the finished surface the new frame will sit on, not temporary or raised internal finishes.

Again we recommend measuring in three places for accuracy.

Measuring your height can be a little trickier. You need to ensure your measurement is taken from the surface that your NEW frame or step will finally sit on.

In this image you can see that the old step protrudes down slightly, therefore the measurement has been taken from the ‘brickwork opening’

Where as you can see the old step in this image has concrete on one side (outside) and tiles on the other (inside) making the inside slightly more elevated. Therefore if you were to measure from the inside on this frame you would be mistakenly INCLUDING the tiles. Summary

• Determine whether you are replacing your Door only, or the door and frame
• Measure the opening and not the existing door or frame
• Include an installation allowance in your measurements ( 3 - 5mm each side of a timber door, or 10mm each side of a new frame)
• Be aware of any excessive interior reductions of the opening size (raised interior floor levels or overly deep plasterboard reveals)
• Compare your sizes to the industry standard sizes available, or the limitations of a made to measure Composite door
• If you are outside of these limitations, can you cut down the product or come down a size and 'pack out' the opening?
• If your opening sizes do not coincide with the information above feel free to get in touch with via Chat (bottom right of screen) and we can guide you!

Once you have your final measurements, you can confidently choose a suitable door size or speak to us for advice if your opening falls outside standard sizes. Accurate measurements also ensure the door can be correctly fitted, sealed, and protected once installed.

For external timber doors, correct sizing works hand-in-hand with correct finishing — see our guide on how to correctly seal an external timber door to prevent moisture ingress and protect your door long term.

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