External Door Sizes: A Guide to Standard UK Sizes

Getting the size right is the first thing to sort out when you're buying a new external door. Whether it's going into an existing opening or a brand-new frame, the door has to match the sizes your home is built around — and, unlike an internal door, it also has to be thick and sturdy enough to stand up to the weather. This guide runs through the standard external door sizes used in the UK, how to measure your opening, and what to do when nothing fits exactly.

The standard UK external door size

If you just want the quick answer: the standard external door size in the UK is 1981 × 838 × 44mm — that's 6'6" tall by 2'9" wide in old imperial money. External doors run a little wider than internal ones, where 762mm (2'6") is the norm, so 838mm (2'9") is the usual width for a front door. Plenty of external openings take a 762mm door too, though — especially older or narrower ones — so both are worth knowing.

From there, a small set of standard sizes covers most openings. Our oak external doors and hardwood external doors come in these standard external door sizes:

These three are the everyday standards, and between them they cover the majority of UK door openings — 838mm (2'9") is the usual width for a front door, with the narrower 762mm (2'6") common on older or more modest entrances. Not every design is made in every size.

Additional sizes we stock

Plenty of homes — especially older or grander ones — need something bigger than the everyday sizes. Alongside the common standards, our range runs to these larger and wider sizes too, so a taller or wider opening doesn't mean a custom door:

These are recognised UK door sizes too, not bespoke one-offs — so a wider 3'0" door or a full 7'0" height is an off-the-shelf choice rather than a special order. Which designs come in which sizes varies, so check the size options listed on the door you like.

Why external doors are 44mm thick

One number stays the same across almost every external door: the thickness. External doors are 44mm thick, where a standard internal door is only 35mm. That extra depth isn't for show — it gives the door the strength to take a heavier lock, resist the wind and hold its shape through wet and dry weather. It's the clearest sign that a door is built for outside rather than in, and it's why an internal door should never be pressed into service as an external one.

How to measure your opening

To find your size, measure the opening the door has to fill — not your old door, which may already have been trimmed down over the years. If you're replacing the door only and keeping the frame, measure the width and height of the frame's inner rebate (the recess the door closes into) in a few places, as older openings are rarely perfectly square. If you're fitting a whole new frame too, measure the structural opening in the wall.

As a rule, order the nearest standard size up from your measurement and trim down to a precise fit, rather than sizing down and leaving a gap you can't close. And remember the frame takes up space of its own: the structural opening always needs to be larger than the door itself once the frame is allowed for.

What if no standard size fits?

Older properties in particular rarely have a bang-on standard opening, so a little adjustment is completely normal. There are three usual routes:

• Trim the door. Timber external doors can be trimmed down for a precise fit — typically around 6–10mm from each edge, depending on the door, as the solid lipping around the edge allows it. Always check the individual door's trimming allowance before you cut.
• Adjust the frame. Frames come as reversible frame-and-cill kits and adjustable vestibule frames, so the opening can be built to suit the door rather than the other way round.
• Go wider, or go double. For an opening wider than a single 915mm door, a pair of doors or a frame with sidelights fills the space while keeping everything in proportion.

Sizing the frame

The frame is sized to the door, not the other way round. Our external door frames are 68mm deep and made to take these standard door sizes, complete with a cill and weather seal at the threshold. If you're setting up a new entrance, pick the frame to match the door size you've chosen, and allow for the frame's own dimensions when you measure the structural opening in the wall.

Front, back and stable doors

External door sizes don't change from the front of the house to the back — a back door uses the same standard sizes as a front door, so you can choose the style you want for each opening without one turning out a different size. Stable doors follow the same overall sizes too; they're simply split into two halves across the middle. Whatever the position, the sizes in the tables above are your starting point.

Choosing your external door

Once you know your size, the rest is style, glazing and timber. Every door is supplied unfinished and trimmable, so you can fit it to your opening and finish it to suit your home — and because the sizes above are standard, you're choosing from an off-the-shelf range rather than paying for a bespoke door.

Frequently asked questions

Get the size right and everything else follows. Browse the full range of oak and hardwood doors in the sizes above on our external doors page — and if you'd like a hand matching a door to an awkward opening, our team is happy to help.

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