Egress Exit Count and Required Width (IBC 1005.3 / 1006.2)
Turns the occupant load into the two egress demands.
Example
You enter
- Occupant load (persons) 160
- Sprinklered AND emergency voice/alarm system (1005.3.1/.2 exceptions) true
- Egress component level
- Minimum door clear width (in) 32
You get
- Exits required 2
- Total egress width 24 in
- Width per exit 32 in
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method.
Details, formula, and sources
ScopeThe number of separate exits (1 up to the Table 1006.3.4(2) single-exit limit -- 49 for a first-story A/B/E/F/M/U, 29 for S, 10 for I/R-1/R-4/H-4/H-5, 3 for H-2/H-3; 29 for B/F/M/S on the second story and none for the rest; none from the third story up -- then 2 to 500, 3 to 1,000, 4 beyond) and the clear width per exit (occupant load x a capacity factor of 0.15 in/occ level or 0.2 in/occ stair when sprinklered, 0.2 / 0.3 without, and for Groups H and I-2 even when sprinklered), divided among the exits and floored at the 32 in door-leaf minimum. For a modest load the exit count and the leaf minimum control, not the raw width. A design aid, not a code-official determination.
Formula or tablefactor = stair ? (sprinklered ? 0.2 : 0.3) : (sprinklered ? 0.15 : 0.2); exits_required = ol <= single_exit_max(group, story) ? 1 : ol <= 500 ? 2 : ol <= 1000 ? 3 : 4 (IBC 2027 Table 1006.3.3(2) [1006.3.4(2) in IBC 2021] single-exit limit: first story 49 A/B/E/F/M, 29 S, 10 I/R-1/H-4/H-5, 3 H-2/H-3; second story 29 for B/F/M/S only; third story and up none; R-3 and R-4 no limit at any story (1006.3.3 item 4); Table 1006.3.2 [1006.3.3 in IBC 2021] beyond); total_width_in = ol x factor; per_exit_in = max(total_width_in / exits_required, min_door_in).
Source and editionIBC 2027 §1005.3 (egress width = occupant load x capacity factor), Table 1006.3.3(2) [1006.3.4(2) in IBC 2021] (single-exit limits by story and occupancy), 1006.3.3 item 4 (R-3 and R-4), Table 1006.3.2 [1006.3.3 in IBC 2021] (2 / 3 / 4 exits), and §1010.1.1.1 [1010.1.1 in IBC 2021] (32 in minimum door clear width), by name.
Free accessThe egress-width and exit-count relations are stated in the published IBC §1005.3 / §1006.2 / Table 1006.3.2 (2027 numbering); the arithmetic is public.
What governsEstimate. AHJ and licensed professional govern.
API field namesoccupant_load, sprinklered, path, min_door_in, exits_required, total_width_in, per_exit_in
- Exit count the Table 1006.3.3(2) single-exit limit for the story and occupancy (R-3 and R-4: one exit at any load), then Table 1006.3.2 (500 / 1,000), sets the number of separate exits, which usually controls a small spaceIBC 2027 Tables 1006.3.2 / 1006.3.3(2) [1006.3.3 / 1006.3.4(2) in IBC 2021]
- Required width occupant load x the §1005.3 capacity factor, divided among the exitsIBC 2027 §1005.3 (unchanged from 2021)
- Door minimum each leaf is floored at the §1010.1.1 32 in clear width; the sprinkler credit cuts the factor by a quarter (level) to a third (stairs)IBC 2027 §1010.1.1.1 [1010.1.1 in IBC 2021]