Internal Door Sizes UK: Standard Widths and the Clear Opening Rule
Internal door sizes in the UK catch people out for one reason: the size printed on the door is not the size of the gap you walk through. The standard British internal door is 1981mm by 762mm, and once it is hung in a lining with a stop, the clear opening is smaller than 762mm. Approved Document M asks for a minimum clear opening width, not a leaf width, and its own note says it takes an 826mm leaf to satisfy the usual 775mm requirement. That single line decides door schedules on a lot of projects.
The common standard: 1981mm high by 762mm wide by 35mm thick, the old 6ft 6in by 2ft 6in, still the default in England and Wales.
The regulation: requirement M4(1) of the Building Regulations 2010, with guidance in Approved Document M Volume 1, which sets a minimum clear opening width.
The note that matters: Approved Document M states that a standard 826mm door leaf up to 44mm thick is deemed to satisfy a requirement for a clear opening width of 775mm.
Corridors are part of the rule: a narrower door needs a wider corridor, and a wider door allows a narrower one. The two are specified together.
The sizes the trade actually sells
Internal doors in England and Wales are still sold in imperial sizes converted to millimetres. The heights are almost always 1981mm; the widths vary.
| Size (mm) | Imperial | Typical use |
|---|---|---|
| 1981 x 610 x 35 | 6ft 6in x 2ft 0in | Cupboards, tight landings |
| 1981 x 686 x 35 | 6ft 6in x 2ft 3in | Small bedrooms, bathrooms in older houses |
| 1981 x 762 x 35 | 6ft 6in x 2ft 6in | The default internal door |
| 1981 x 838 x 35 | 6ft 6in x 2ft 9in | Where a wider clear opening is needed |
| 2040 x 726 x 40 | Metric | Standard in Scotland and much of Europe |
| 2040 x 826 x 40 | Metric | The metric wide leaf |
External doors are a different standard again, commonly 1981mm by 838mm by 44mm. Fire doors are usually 44mm thick rather than 35mm, which matters for both the frame and the clear opening.
Clear opening width is not leaf width
Approved Document M measures the clear opening width of a doorway, which is the usable gap with the door open, not the width of the leaf. The door swings back into the opening, and the stop on the far side takes a few more millimetres, so a 762mm leaf gives a clear opening in the region of 700mm to 720mm depending on the lining, the stop and the thickness of the door. That is why the guidance carries the explicit note that a standard 826mm leaf up to 44mm thick is deemed to satisfy a 775mm clear opening. If you specify 762mm doors and then discover the drawing says 775mm clear, the doors are wrong, not the drawing.
The door and corridor table
Approved Document M does not set a single door width. It sets pairs: a doorway clear opening width and the corridor width that goes with it. The same table appears at Table 1.1 for M4(1) visitable dwellings and Table 2.1 for M4(2) accessible and adaptable dwellings.
| Doorway clear opening width | Corridor clear passageway width |
|---|---|
| 750mm or wider | 900mm, when approached head on |
| 750mm | 1200mm, when the approach is not head-on |
| 775mm | 1050mm, when the approach is not head-on |
| 800mm | 900mm, when the approach is not head-on |
Read it the other way round and it becomes a design tool. If a hallway is tight and the approach is sideways, widening the door reduces the corridor width you need. An 800mm clear opening brings the requirement back down to 900mm of corridor, where a 750mm opening would demand 1200mm.
Halls, obstructions and nibs
The guidance for M4(2) dwellings also covers what is around the door. The minimum clear width of every hall or landing is 900mm. A localised obstruction such as a radiator must not sit opposite or close to a doorway or at a change of direction, must be no longer than 2m, and must not reduce the corridor below 750mm at any point. And a minimum 300mm nib is required to the leading edge of every door within the entrance storey, so that someone can get alongside the handle. That nib is the detail most often lost when a designer pushes a door hard into a corner.
For M4(3) wheelchair user dwellings the numbers step up again: every door needs a clear opening width of 850mm regardless of the direction of entry, every hallway, approach or landing needs 1050mm, and 1200mm where the approach to a doorway is not head-on, with a 300mm nib to the leading edge and 200mm to the following edge of every door.
When does any of this apply to your house?
This is the part worth being straight about. Approved Document M Volume 1 applies to new dwellings. M4(1) is the baseline standard for new homes; M4(2) and M4(3) apply only where a planning condition imposes them, which is common in London boroughs and rare elsewhere. If you are moving a stud wall in an existing Victorian terrace, Part M is generally not what determines your door widths.
What it is, in that case, is a good specification to borrow. The clear opening figures are the widths at which a house stops feeling pinched: a wheelchair, a pushchair, a sofa and two people carrying a wardrobe all benefit from the same dimensions. On period property work we specify to the M4(2) numbers wherever the existing structure allows it, because it costs nothing at design stage and is expensive to retrofit. Building control will confirm what applies to your particular job, and it is worth asking before the door schedule is signed off rather than after.
Two practical points for older houses. First, original openings in Victorian and Edwardian houses are often wider than 762mm, so measure before assuming you need a standard door; a made-to-measure leaf is frequently the right answer. Second, if you are fitting fire doors to a loft conversion or a three-storey house, the 44mm leaf and the intumescent seals both eat into the clear opening, so specify the wider leaf from the start.
For the dimensions that govern the rooms those doors open into, see our guides to minimum bedroom sizes, kitchen dimensions and clearances and minimum ceiling heights, and our overview of building regulations for a London renovation. Or start at Vertigo Interiors.
Frequently asked questions
What is the standard internal door size in the UK?
1981mm high by 762mm wide by 35mm thick is the default in England and Wales, the metric equivalent of 6ft 6in by 2ft 6in. Scotland and much of Europe use metric sizes, commonly 2040mm high and 726mm or 826mm wide at 40mm thick.
Is a 762mm door wide enough for Part M?
Not on its own. Approved Document M measures clear opening width rather than leaf width, and its own note states that a standard 826mm leaf up to 44mm thick is deemed to satisfy a requirement for a 775mm clear opening. A 762mm leaf gives a smaller clear opening once it is hung.
What is clear opening width?
The usable gap with the door open, measured from the face of the open leaf to the opposite stop. It is always less than the leaf width, because the open door and the stop both intrude into the opening.
How wide does the corridor have to be?
It depends on the door. Approved Document M pairs them: a 750mm clear opening needs 900mm of corridor head on or 1200mm if the approach is sideways, 775mm needs 1050mm sideways, and 800mm needs only 900mm sideways.
What size door does a wheelchair user dwelling need?
Under M4(3), every door needs an 850mm clear opening width irrespective of the direction of entry, with hallways, approaches and landings at 1050mm minimum and 1200mm where the approach to a doorway is not head-on.
Do these rules apply when I renovate an existing house?
Usually not directly. Approved Document M Volume 1 governs new dwellings, and M4(2) and M4(3) only apply where a planning condition requires them. The figures are still the right specification to design to where the structure allows, and your building control body will confirm what applies to your project.
Sources
- Approved Document M: access to and use of buildings, Volume 1, for Table 1.1 and Table 2.1 pairing doorway clear opening widths with corridor widths, the note that a standard 826mm leaf up to 44mm thick satisfies a 775mm clear opening, the 900mm hall width and 300mm nib at M4(2), and the 850mm and 1050mm figures at M4(3)
Checked on 16 September 2026. Guidance applies to England; Wales and Scotland have their own standards. Confirm what applies to your project with your building control body before the door schedule is fixed.