Internal Door Sizes & Standard Widths: UK Guide

The UK’s internal door market uses metric nominal sizes that map directly to the old imperial measurements, a legacy of the industry transitioning from feet and inches without fully abandoning the traditional dimensions. Knowing the conventions prevents expensive ordering mistakes, particularly in older properties where openings were framed to imperial standards.

The standard door leaf height across all modern UK internal doors is 1981 mm (6 ft 6 in). Widths are less uniform and choosing the wrong one requires either cutting the door down or having a bespoke door made.

Standard Internal Door Sizes (UK, 2026)

The 762 mm (2’6”) wide door is by far the most commonly stocked size in UK builders’ merchants and DIY stores. If you are ordering a door speculatively for a property you have not yet measured, this is the safest single-size guess, but always measure before buying.

For double doors (pairs), each leaf is typically 686 mm or 762 mm wide to give a combined opening of approximately 1372 mm or 1524 mm.

Non-Standard Heights

Older UK properties, particularly Victorian and Edwardian terraces, frequently have door openings that were framed taller than 1981 mm. Common non-standard heights include:

• 2032 mm (6’8”), frequently found in 1920s–1950s build stock
• 2040 mm, some 1960s–1980s social housing
• 2083 mm (6’10”), a common Victorian height
• 2134 mm (7’0”), high-ceilinged Victorian and Georgian properties

Most door suppliers offer 2040 mm or 2040 mm × standard widths as a secondary stock size. Above 2040 mm, you are typically into bespoke territory. Expect to pay a 20–60% premium over standard-sized equivalents for non-standard heights from specialist joinery suppliers, or to have a standard door extended by a joiner (add a head panel or frame extension, cost approximately £80–£200 per door).

Measuring an Existing Opening

Always measure the structural opening (the masonry or studwork opening) rather than the existing frame or the door leaf itself, then work backwards:

1. Measure the structural opening width in three places: top, middle, and bottom. Use the smallest dimension.
2. Subtract the frame thickness: a standard lining set uses 25–32 mm linings each side, so deduct 60–64 mm from the structural width to get the door leaf width.
3. Account for reveal depth: standard 35 mm door linings are designed for a 105 mm thick stud wall. Solid walls will need a wider lining, specify the reveal depth (wall thickness including plaster) when ordering.
4. Allow 2–3 mm clearance between door leaf and lining on each side and 3 mm at the bottom (over carpet) or 8–10 mm (over thick carpet with underlay).

A quick rule of thumb: structural opening width minus 100 mm = approximate door leaf width for a 35 mm lining set.

Wheelchair Access and Part M

Building Regulations Approved Document M (Access to and Use of Dwellings) sets minimum door widths for accessibility:

Clear opening width is measured from the door face to the door stop with the door open 90°, not the nominal door leaf width. A 762 mm leaf in a standard frame gives approximately 730–740 mm clear, just below M4(1). An 838 mm leaf typically gives around 800–810 mm clear, meeting M4(2) and M4(3).

For existing properties undergoing extension or significant refurbishment, check with Building Control whether Part M applies to the project scope, it is not automatic for like-for-like replacements but does apply to newly created habitable rooms.

Door Thickness

UK internal doors are almost universally 35 mm thick (for residential). Some hollow-core budget doors are 40 mm; some solid hardwood or fire-rated doors are 44 mm. Always check the door stop rebate in the frame if replacing a door without replacing the frame, a 44 mm door in a 35 mm rebate will not close properly.

FD30 fire doors (30-minute fire resistance) must be at least 44 mm thick in solid-core construction. They require self-closing gear and intumescent strip around the perimeter. These are required under Part B of the Building Regulations for doors into integral garages and for protected escape routes in three-storey or taller dwellings.

Costs (2026 Supply Only)

Fitting by a joiner (hanging, trimming, hardware) typically adds £80–£180 per door depending on location and door weight.

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.