Our interactive Clear Opening Widths Calculator below allows you to work out the Clear Opening Width, Leaf Width, Frame Width or Structural Opening Width for a number of varied door constructions.

To use the Calculator, click on Filter 1 for the Leaf Configuration, Filter 2 for the Leaf Action, and Filter 3 for the Known Dimensions for the required construction. The resulting dimensions are then shown highlighted in green in the Output Form below. Default dimensions are provided in the orange boxes and can be amended by typing in the required data. Fixed dimensions are shown in the white boxes. Results will be calculated automatically by default.

Please note, the actual door leaf width required to ensure the correct 'Effective Clear Width' as identified in Approved Document M and BS8300-2: 2018, will depend on the combination of several variables for reference:

- Leaf thickness
- Rebate/stop depth
- Hinge knuckle diameter
- Ironmongery projection (e.g. lever handle, pull handle etc)