Evacuation Time Estimator
Estimate how long it takes to clear a space using the simple hydraulic model: total time = travel time to the exit plus flow (queue) time through the exit. Enter the occupant count and effective exit width for a first-pass egress figure in minutes and seconds.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the number of occupants and the total effective exit width in metres (the clear width less edge allowances).
- Adjust the specific flow rate if needed (default 1.3 persons/m/s, a typical level-exit maximum).
- Optionally add the travel distance to the exit and walking speed (default 1.2 m/s) to include travel time. Read the total in min:sec and seconds.
How it works
Two components are added. Flow (queue) time = occupants / (effective exit width × specific flow rate) — how long the crowd takes to pass through the doorway. Travel time = travel distance / walking speed — how long to reach the exit. The total is travel time + flow time. Defaults of 1.3 persons/m/s and 1.2 m/s reflect common unimpeded values, but the model ignores stairs, merging flows, bottlenecks and pre-movement time.
Worked example
Worked example. 200 people leave through 2 m of effective exit width at 1.3 persons/m/s: flow time = 200 / (2 × 1.3) = 76.9 s. If the furthest person walks 30 m at 1.2 m/s, travel time = 30 / 1.2 = 25 s. Total ≈ 101.9 s, or about 1 minute 42 seconds.
Common mistakes
- Using the physical door width instead of the EFFECTIVE width. Boundary-layer allowances at each edge reduce the usable width and increase the flow time.
- Treating the result as a real evacuation time. It ignores stairs (which flow slower), merging flows, and pre-movement/reaction time, so actual clearance is usually longer.
- Forgetting travel time for large or deep spaces. With long travel distances the walk to the exit can dominate the flow time — include the distance and speed.
Frequently asked questions
What specific flow rate should I use?
About 1.3 persons/m/s is a common maximum for a level exit and is the default. Stairs and downward travel are slower, and crowd density changes the figure. For anything critical, use the values and method from a recognised source such as the SFPE hydraulic model.
Can I rely on this for a building's fire safety design?
No. This is a simplified first-pass estimate only. A real design needs a fire-engineering evacuation analysis (merging flows, door and stair capacities, behaviour, pre-movement time) by a competent fire engineer, and must satisfy the building code and your regulator.
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