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Egress Width Calculator

Work out egress width instantly with clear inputs, formula shown and shareable results.

About Egress Width Calculator

Egress width is the occupant load multiplied by a capacity factor, conventionally 5 mm per person for level travel and 8 mm for stairs, divided between the available exits and never less than the code minimum clear width. Codes also require the remaining exits to serve the full load if the largest is discounted.

Formulas

Egress width

Total mm = occupants x width per person; per exit = total / exits, not less than the minimum

Redundancy

Check total / (exits - 1) with the largest exit discounted

Worked example

With the default values below, Egress Width Calculator returns Clear width required per exit of 900. Change any input above and every figure here is recalculated in your browser.

Inputs used

Occupant loadminimum 1 people
300 people
Width per occupantminimum 1 mm
5 mm
Number of exitsminimum 1
2
Minimum clear width per exitminimum 100 mm
900 mm

Results

Clear width required per exit
900 mm
Total egress width required
1,500 mm
Occupants served per exit
150 people
Width needed if one exit is blocked
1,500 mm

Step by step

  1. 1Values used
  2. 2Egress width
  3. 3Redundancy
  4. 4Clear width required per exit= 900 mm
  5. 5Total egress width required= 1,500 mm
  6. 6Occupants served per exit= 150 people
  7. 7Width needed if one exit is blocked= 1,500 mm

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Means of escape must be designed to the fire and building code adopted locally and verified by a qualified fire engineer.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Means of escape must be designed to the fire and building code adopted locally and verified by a qualified fire engineer.

Frequently Asked Questions

How is the Egress Width figure worked out?

Total mm = occupants x width per person; per exit = total / exits, not less than the minimum. Egress width is the occupant load multiplied by a capacity factor, conventionally 5 mm per person for level travel and 8 mm for stairs, divided between the available exits and never less than the code minimum clear width.

Why is stair width per person greater?

People move more slowly and less densely on stairs, so the same flow rate needs more width. That is why stair capacity factors are roughly 60 percent higher than for level routes.

What values do I need to enter?

This calculator takes 4 inputs: Occupant load, Width per occupant, Number of exits, Minimum clear width per exit. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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