| Primary value | 5 mm/person ((stairs); 7.5 mm/person (doorways)) |
| Applies to | All occupancies — residential, commercial, assembly |
| Exceptions | Stairways → 5 mm per person |
| Doorways and corridors → 7.5 mm per person | |
| Min stair width (residential) → 1.0 m | |
| Min stair width (other) → 1.5 m | |
| Ramps → 8.33 mm per person (60 persons per 500 mm unit width) | |
| Stairs in fully sprinklered buildings > 70m high → 6.67 mm per person (capacity increased to 75 persons per unit width) | |
| Measured as | Required total exit width = occupant load × per-person factor. Provide as one or multiple stairs/doors. |
| Source | NBC 2016 — Part 4, Clause 4.4 and Table 7 ✓ Verified |
These factors are derived from the 'unit of exit width' concept in NBC 2016, which quantifies the flow rate of people during an emergency. Adhering to these widths is critical for preventing dangerous bottlenecks and crowd crush during evacuation, forming a fundamental pillar of the code's life safety provisions.
For a 200-person commercial floor, the required total stair width is 200 × 10 mm = 2000 mm. This must be provided via at least two separate staircases (as per Clause 4.5), for example, two stairs of 1.0 m width each. The total required door width would be 200 × 6.67 mm ≈ 1334 mm.