Quick Answer: What Is the Standard Door Size in the UK?
The standard internal door size in the UK is 1981mm by 762mm (78 inches by 30 inches), though 686mm and 838mm widths are also common depending on the room. Standard external door sizes are typically 1981mm by 838mm. Door thickness is usually 35mm for internal doors and 44mm for external doors, which affects fire rating and weatherproofing performance.
Standard Internal Door Sizes UK
| Door Size (Height x Width) | Imperial Equivalent | Typical Use |
|---|---|---|
| 1981mm x 610mm | 78″ x 24″ | Small cupboards, narrow spaces |
| 1981mm x 686mm | 78″ x 27″ | Bathrooms, smaller rooms |
| 1981mm x 762mm | 78″ x 30″ | Most common standard internal door |
| 1981mm x 838mm | 78″ x 33″ | Bedrooms, living rooms, wider openings |
Standard External Door Sizes UK
External doors are typically taller and wider than internal doors to accommodate frames, weather seals, and thicker construction. The most common external door size is 1981mm by 838mm, with a thickness of 44mm, compared to the 35mm thickness typical of internal doors.
Door Thickness Explained
- 35mm: Standard for most internal doors
- 40mm: Used for some fire rated internal doors, such as FD30 rated doors between a garage and a house
- 44mm: Standard for external doors, providing better weatherproofing and security
How to Measure a Door Opening Accurately
- Measure the height of the opening at three points across its width, using the smallest measurement if they differ
- Measure the width at the top, middle, and bottom of the opening, again using the smallest measurement
- Check the opening for square by measuring both diagonals corner to corner. If they match, the opening is square
- Measure the depth of the wall to confirm the correct door lining or frame depth needed
Older properties, particularly those built before standardised sizing became common, may have openings that do not match modern standard sizes, in which case a made to measure door or frame adjustment will be needed — or, for internal openings, an internal bifold door kit sized to the full opening.
Standard Door Width by Room Type
| Room | Typical Door Width | Notes |
|---|---|---|
| Bathroom / WC | 686mm | Narrower doors common for smaller rooms |
| Bedroom | 762mm to 838mm | Standard width for general use |
| Living room / hallway | 838mm or wider | Wider for easier furniture movement |
| Cupboard / airing cupboard | 457mm to 610mm | Narrower, often bifold or single panel |
| Front / back external door | 838mm | Standard external width |
Accessibility and Wider Doorways
Building Regulations Part M sets accessibility requirements for new build and some renovation projects, generally recommending a minimum clear opening width of 775mm for accessible doorways, which is wider than some older standard doors provide once the frame and door thickness are accounted for. This is worth considering if accessibility is a priority for any current or future occupant.
Non-Standard and Bespoke Door Sizes
Period properties, loft conversions, and older extensions often have openings that fall outside standard sizing. In these cases, options include a bespoke made to measure door, adjusting the opening itself to fit a standard size, or using an oversized standard door trimmed down slightly, which is only suitable within certain tolerances before it affects the door’s structural integrity or fire rating.
Frequently Asked Questions
What is the most common internal door size in the UK?
1981mm by 762mm is the most widely used standard internal door size across UK housing, fitting most bedroom, living room, and general purpose openings.
How do I know what size door I need?
Measure the existing opening’s height and width at multiple points, using the smallest measurement in each direction, then compare against standard sizes to find the closest match, or consider a bespoke door if the opening falls significantly outside standard dimensions.
Are external doors a different thickness to internal doors?
Yes, external doors are typically 44mm thick compared to the standard 35mm for internal doors, providing better weatherproofing, security, and structural strength against the elements.
What size door frame do I need for a standard door?
A standard door frame or lining typically adds around 40 to 45mm to each side of the door leaf dimensions to accommodate the frame itself, so always check the specific product’s overall kit size, not just the door leaf size.
Can I fit a standard door in an older, non-standard opening?
In many cases yes, either by adjusting the opening slightly or using packing pieces around a standard frame, though significantly undersized or oversized openings may require a bespoke door instead.
Expert Insight
Joiners consistently recommend checking a door opening for square before ordering any door, since even a standard sized door will not fit or close properly in an opening that has moved out of square over time, which is common in older properties as a building settles.
Final Thoughts
Knowing UK standard door sizes makes it much easier to plan a renovation, order replacement doors with confidence, and spot when an opening will need a bespoke solution instead. Always measure the actual opening rather than assuming standard sizing, particularly in period properties.
Ordering a replacement door? Take photos of your measurements alongside a tape measure for your own records, which makes it much easier to resolve any sizing queries with a supplier later.
Written by the HometoWorld editorial team, covering home improvement, renovation, and property maintenance across the UK.
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