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The area whose occupants use these routes, not the whole building.
Take one storey, or one part of a storey separated from the rest by fire-resisting construction, and count only the area whose occupants would actually reach these doors. A floor with two independent escape strategies is two calculations. Where a code asks for gross area, include the circulation and stores; where it asks for net, take the occupied space only — the two can differ by a third on the same drawing.
The density figure for the building's use, from the code you work to.
This is the single input that moves the answer most, and the figures are not close between code families: an office is commonly taken at 6 m² (about 65 sq ft) per person under one, and at 14 m² (about 150 sq ft) gross under another. Standing bars, assembly space and classrooms are far denser again — under 1 m² (about 10 sq ft) per person is normal for standing areas. Use the table in force where you build, and where a floor holds more than one use, work each part separately rather than averaging them.
How many independent ways out this area has.
Independent means what it says: two doors into the same corridor are one route, because one fire closes both. Count only routes that reach a final exit or a protected stair by separate paths. Entering 1 leaves nothing to discount, and the page then sizes that single route for everyone — which is what a code permits only for small, low-risk areas with a short travel distance.
The clear width each person is allowed, from your code's table.
Level routes and doors are commonly taken at 5 mm (about 0.2 in) per person, and stairs at a larger figure because people move down them more slowly. Some codes reduce both where the building is sprinklered and alarmed. This page applies one figure to one kind of route, so size a stair with the stair figure rather than folding it into the same sum.
The floor below which a route may not go, however few people use it.
Codes set a floor that has nothing to do with the occupant load — commonly around 750 to 850 mm (about 30 to 33 in) for a door serving a small number, rising in steps as the number served rises. It exists because a route narrower than that does not work for a stretcher, a wheelchair or two people passing, whatever the arithmetic says. Below a hundred or so occupants this minimum usually governs the answer outright.
Clear width of each remaining route
33 in
83 occupant(s) over 1 route(s) after discounting the largest, so 83 per route. The minimum width governs here, not the occupant load.
- Occupants served
- 83 people
- Routes counted after the discount
- 1 route
- People per remaining route
- 83 people
- Width the occupant load alone asks for
- 16.6 in
- Minimum width that applies
- 33 in
- Total clear width across the remaining routes
- 33 in
They open the calculator with your figures already in it
Occupant Load and Escape Route Width Calculator: 33 in — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Occupant load is the floor area served divided by the area per person for the use — a density figure published per building type, not a headcount anyone takes on the day
- Escape route width is the occupant load multiplied by a width per person, subject to a minimum width that applies however few people are served
- The largest escape route is discounted and the remaining routes sized for the whole occupant load, because a fire can block any single exit — the same reasoning that puts two ways out of a room in the first place
Inputs used
- Floor area the routes serve
- 5380 sq ft
- Area per person for the use
- 65 sq ft
- Escape routes provided
- 2
- Width per person
- 0.2 in
- Minimum width that applies
- 33 in
Intermediate steps
- Occupants served
- 83 people
- Routes counted after the discount
- 1 route
- People per remaining route
- 83 people
- Width the occupant load alone asks for
- 16.6 in
- Minimum width that applies
- 33 in
- Total clear width across the remaining routes
- 33 in
Confidence note: 83 occupant(s) over 1 route(s) after discounting the largest, so 83 per route. The minimum width governs here, not the occupant load.
What this calculation does not cover
- WIDTH ONLY. Travel distance is the other half of means of escape and this page does not see it: a route of ample width that is too long is not an escape route, and no floor area can tell you how far anyone walks. Door swing, headroom, the protected stair's own capacity and where the final exit discharges all sit outside this too.
- The discount removes ONE route, which is the common rule and not a universal one. Some codes discount by capacity rather than by count, some require more than one to be discounted above a threshold, and some let a sprinklered building discount none. The page applies the rule you chose by entering the number of routes.
- Area per person is a published density for a use, not a headcount. A room fitted out for forty and licensed for a hundred is a hundred, and a floor whose use changes has a new occupant load the day it changes, with no building work to mark the moment.
- One figure, one kind of route. Stairs are sized on a larger width per person than level routes because people descend more slowly, so a stair worked out with a level-route figure comes back narrow. Work the stair separately with its own number.
- THIS COMPARES A WIDTH AGAINST RULES YOU SUPPLIED. It is not a compliance check and cannot be one — the figures that matter most here are exactly the ones that differ between jurisdictions, building types and fire engineering strategies.
Add the equipment this sizes
This result is a specification — 33 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-23 · v1.0.0
Regulatory standards & verification citations3
- Occupant load is the floor area served divided by the area per person for the use — a density figure published per building type, not a headcount anyone takes on the day
- Escape route width is the occupant load multiplied by a width per person, subject to a minimum width that applies however few people are served
- The largest escape route is discounted and the remaining routes sized for the whole occupant load, because a fire can block any single exit — the same reasoning that puts two ways out of a room in the first place
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