Evacuation Time Calculator

Estimates total building/area evacuation time from occupant load and exit width, using the SFPE (Society of Fire Protection Engineers) hydraulic flow-calculation approach: pre-movement time + travel time + exit queuing/discharge time.

Occupancy & Exits

Total Occupant Load Total number of people to be evacuated from the area/floor/building.

Number of Usable Exits Assumes occupants distribute evenly across all usable exits.

Exit Component Type Sets the specific flow rate and typical boundary layer loss — both remain editable.

Clear Width per Exit (mm) Measured clear/unobstructed width of each exit opening.

Boundary Layer Loss (mm) Width lost to wall/edge effects (people don't use the full physical width).

Specific Flow Rate (persons/min per metre of effective width) Default per IBC/SFPE: ~78.7 for doors/corridors, ~59.1 for stairs.

Timing Factors

Pre-Movement Time (s) Detection + alarm + human response/decision time before movement begins.

Average Travel Distance to Exit (m)

Average Walking Speed (m/s) Typical unimpeded walking speed: 1.0–1.2 m/s; reduce for mobility-impaired occupants or smoke conditions.

0.0

Exit Queuing Time (s)

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Travel Time (s)

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Total Evacuation Time (s)

Formula Reference

Effective Width per Exit = Clear Width − Boundary Layer Loss
Exit Flow Capacity = (Effective Width × Number of Exits) × Specific Flow Rate
Exit Queuing Time = Occupant Load ÷ Flow Capacity
Travel Time = Travel Distance ÷ Walking Speed
Total Evacuation Time = Pre-Movement Time + Travel Time + Exit Queuing Time

Doors / Corridors (IBC/SFPE)	~78.7 persons/min per metre width (24/ft/min)
Stairways (IBC/SFPE)	~59.1 persons/min per metre width (18/ft/min)
Typical boundary layer loss	150–200 mm per exit, per SFPE Handbook

Benchmark Guidance

There is no single universal pass/fail time — acceptable evacuation time depends on occupancy type, building complexity, and applicable code. As a general reference point, BS 9999 (British Standard for fire safety in building design) suggests around 2.5 minutes for low-complexity buildings, up to 5 minutes for more complex ones; many workplace fire risk assessments target under 3 minutes for straightforward office/industrial layouts. Always confirm the applicable target against your local fire code and a qualified fire safety engineer.

Methodology, interpretation & sources

Purpose. Estimates total building/area evacuation time from occupant load and exit width, using the SFPE (Society of Fire Protection Engineers) hydraulic flow-calculation approach: pre-movement time + travel time + exit queuing/discharge time.

How to use the result. Start with source data you can verify, enter values on a consistent unit and time basis, and record the assumptions used. The main inputs on this page include Total Occupant Load Total number of people to be evacuated from the area/floor/building., Number of Usable Exits Assumes occupants distribute evenly across all usable exits., Exit Component Type Sets the specific flow rate and typical boundary layer loss — both remain editable., Clear Width per Exit (mm) Measured clear/unobstructed width of each exit opening., Boundary Layer Loss (mm) Width lost to wall/edge effects (people don't use the full physical width)., Specific Flow Rate (persons/min per metre of effective width) Default per IBC/SFPE: ~78.7 for doors/corridors, ~59.1 for stairs.. Re-run the calculation when those assumptions change rather than carrying an old result forward.

Decision use. Use this tool as a planning estimate and confirm the final control or design with a competent person using site measurements, manufacturer data and applicable construction requirements.

Limitations. Ground conditions, equipment configuration, dynamic loading, access, weather and work sequencing can materially change the safe limit.

Primary references. Use the current edition/version that applies to your jurisdiction and organization:

Editorial note. Prepared and maintained by Impact Tech Solutions. Editorially updated 28 September 2026. No individual professional credential is claimed on this page; high-consequence, statutory, tax, engineering or health decisions should be independently verified against the current primary source and, where required, a qualified professional.