TradeCalculator.co.uk
Door Width Calculator - Part M Effective Clear Width
Calculate effective clear door widths for wheelchair access per Approved Document M Vol 2 (Table 2) and BS 8300-2:2018.
Width of the door leaf (panel), not the structural opening
44mm standard / FD30, 54mm for FD60. The leaf projects into the opening when open at 90°
If the door swings past 90° and no furniture obstructs, the projecting handle is not deducted
How far handles/locks project from the door face (deducted at 90° open)
Height of any threshold or upstand (0 for level). AD M para 2.7e: max 15mm
AD M para 3.10a: ≤ 30N at the leading edge (0-30°), ≤ 22.5N (30-60°)
Optional reveal/structural opening size — recorded only; does not affect the effective clear width
Next up: related pages
How We Calculate This
This calculator determines the effective clear width of a door opening and checks compliance with Approved Document M Vol 2 (Access to and use of buildings other than dwellings) and BS 8300-2:2018.
Effective clear width calculation
AD M measures the effective clear width from the outside of the door stop on the closing side to any obstruction on the hinge side — which, for a hinged door open to 90°, is the door leaf itself. For a single hinged door at 90°: Effective Clear Width = Leaf Width − Door Stop − Leaf Thickness − Ironmongery Projection. The door stop is typically 25-30mm; the leaf is 44mm (standard/FD30) or 54mm (FD60). If the door opens beyond 90° and no furniture obstructs, the projecting handle is no longer deducted.
Part M required widths (AD M Vol 2 Table 2)
- Straight-on, or right angles to a route ≥ 1500mm: 800mm new / 750mm existing
- Right angles to a route ≥ 1200mm: 825mm new / 775mm existing
- External door, building used by the public: 1000mm new / 775mm existing
- Leading edge: 300mm unobstructed space on the pull side (Diagram 9)
- Threshold: level preferred, 15mm maximum, upstands > 5mm chamfered/rounded (para 2.7e)
- Opening force: ≤ 30N at 0-30°, ≤ 22.5N at 30-60° (para 3.10a internal / 2.17a entrance)
Standard UK door leaves (90° open, 44mm leaf, 20mm furniture)
Indicative only — confirm against the specific doorset’s tested clear opening.
- 726mm (2'6") — ~635mm clear — below 800mm
- 826mm (2'9") — ~735mm clear (~755mm beyond 90°) — below 800mm
- 926mm (3'0") — ~835mm clear (~855mm beyond 90°) — compliant for 800/825mm
- 1026mm (3'3") — ~935mm clear (~955mm beyond 90°) — compliant for 800/825mm, but short of the 1000mm public-entrance figure (use a wider leaf or a leaf-and-a-half set)
Frequently Asked Questions
It depends on how the door is approached. Approved Document M Vol 2 Table 2 sets the minimum effective clear width as 800mm for a straight-on approach or where the door is at right angles to an access route at least 1500mm wide; 825mm where the door is at right angles to a route at least 1200mm wide; and 1000mm for external doors to buildings used by the general public. The corresponding figures for existing buildings (reasonable provision) are 750/750/775/775mm. Note this is the effective clear opening with the door open, not the door leaf size.
The door leaf width is the full width of the door panel. The effective clear width is the actual usable opening, measured from the outside of the door stop on the closing side to any obstruction on the hinge side. When a hinged door is open to 90°, that obstruction is the door leaf itself, so you deduct the door stop (about 25-30mm), the door leaf thickness (44mm for a standard/FD30 leaf, 54mm for FD60) and any projecting door furniture. A 926mm leaf open to 90° with a 44mm thickness and a projecting handle gives roughly 835mm clear; opened beyond 90° with no obstructing furniture it gives roughly 855mm. Confirm the figure against the specific doorset’s tested clear opening.
A nib is the wall space between the door frame and any adjacent return wall on the leading (pull) side of the door. Approved Document M Vol 2 (Diagram 9) requires at least 300mm of unobstructed space on the pull side, between the leading edge of the door and any return wall, unless it is a powered entrance door. This lets a wheelchair user position alongside the door to reach and operate the handle without being blocked by the door swing.
Approved Document M Vol 2 (para 2.7e) says the threshold should be level or, if a raised threshold is unavoidable, have a total height of not more than 15mm, with any upstand higher than 5mm chamfered or rounded. (The older 13mm figure came from the withdrawn BS 8300:2009 weatherbar detail and is not in current AD M.) Any height above 15mm creates a trip hazard and a barrier for wheelchair users.
Related Calculators
Was this calculator helpful?
Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.