Evacuation Time
Estimate the evacuation time of a space, t = N ÷ (F × width), dividing the number of occupants N by the product of the specific people flow F (people per minute per metre) and the total exit width (m). The result, in minutes, is the movement time for everyone to pass through the exits — part of the total egress time used in escape route design and fire safety verification. Adequate exit widths and flows ensure evacuation occurs before conditions become untenable. Enter the number of occupants, the specific flow and the exit width.
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Evacuation time
In fire safety, the golden rule is that the available time for escape (until conditions turn untenable from smoke, heat or gases) must exceed the required time for everyone to get out. This calculation estimates the movement share of that required time: t = N ÷ (F × width), the occupant count N divided by the discharge capacity of the exits, which is the specific flow F (people per minute per meter of width) times the total width of the exits. The result, in minutes, is how long the crowd takes to get through the doors and stairs, assuming continuous flow. Typical specific flow in horizontal circulation runs on the order of 40–80 people/min/m, dropping on stairs (where movement is slower). Note that the total egress time still includes the detection and alarm time, the pre-movement time (people recognizing the threat and deciding to act — often the largest component!) and the travel time to the exits. This calculation isolates the exit bottleneck: a high result signals that the exits are too narrow for the occupant load — they must be widened or extra exits provided. Enter the number of occupants, the specific flow and the total exit width.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.