Door Width Calculator - Part M Effective Clear Width
Calculate effective clear door widths for wheelchair access per Approved Document M and BS 8300.
Width of the door leaf (panel), not the opening
Structural wall thickness at the door opening
How We Calculate This
This calculator determines the effective clear width of a door opening and checks compliance with Approved Document M (Access to and use of buildings) and BS 8300:2018.
Effective clear width calculation
For a single hinged door: Effective Clear Width = Leaf Width - Door Stop - Ironmongery Projection. The door stop is typically 25-30mm. Ironmongery (handles, locks) may project 15-25mm from the door face.
Part M requirements
- New buildings: 800mm minimum effective clear width
- Existing buildings: 750mm minimum (reasonable provision)
- Side approach: 300mm nib required on pull side
- Threshold: Level preferred, 13mm maximum (15mm with chamfer)
Standard UK door sizes
- 726mm (2'6") - ~679mm clear - Not compliant
- 826mm (2'9") - ~779mm clear - Marginal
- 926mm (3'0") - ~879mm clear - Compliant
- 1026mm (3'3") - ~979mm clear - Compliant
Frequently Asked Questions
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Last updated: March 2026
All calculations are estimates. Verify with your supplier.