Code Compliance
Egress Path Basics
A guide to calculating occupancy loads and required exit widths. Understand the math behind means of egress design and avoid common code review comments.
The Core Formulas
Step 1: Calculate Occupant Load
Occupant Load = Area ÷ Load Factor
Example: 3,000 SF office ÷ 150 SF/person = 20 occupants
Step 2: Calculate Exit Width
Exit Width = Occupants × Multiplier
Example: 300 people × 0.15"/person = 45" total exit width
Occupancy Load Factors (IBC Table 1004.5)
| Use Type | Load Factor | Notes |
|---|---|---|
| Assembly (concentrated, no fixed seats) | 7 sq ft/person | Standing/waiting areas |
| Assembly (unconcentrated) | 15 sq ft/person | Dining, conference rooms |
| Assembly (fixed seating) | Number of seats | Theaters, auditoriums |
| Business | 150 sq ft/person | Offices |
| Educational (classroom) | 20 sq ft/person | Teaching areas |
| Educational (shops/labs) | 50 sq ft/person | Vocational areas |
| Industrial | 100 sq ft/person | Manufacturing |
| Institutional (inpatient) | 240 sq ft/person | Sleeping areas |
| Institutional (outpatient) | 100 sq ft/person | Treatment areas |
| Library (reading rooms) | 50 sq ft/person | Study areas |
| Library (stack areas) | 100 sq ft/person | Book storage |
| Mercantile (basement/ground) | 30 sq ft/person | Retail sales |
| Mercantile (upper floors) | 60 sq ft/person | Upper floor retail |
| Residential | 200 sq ft/person | Dwelling units |
| Storage (warehouse) | 300 sq ft/person | Low hazard |
| Accessory storage | 300 sq ft/person | Mechanical rooms |
Exit Width Multipliers
| Component | Sprinklered Building | Non-Sprinklered |
|---|---|---|
| Doors, Corridors, Ramps | 0.15" per person | 0.2" per person |
| Stairs | 0.2" per person | 0.3" per person |
Pro Tip: Sprinklered buildings allow narrower exits because sprinklers slow fire growth, giving occupants more evacuation time. Always use 0.15" and 0.2" for sprinklered buildings.
Worked Example: Restaurant
Given
4,500 SF dining area (unconcentrated assembly) in a sprinklered building
Step 1: Calculate Occupant Load
4,500 SF ÷ 15 SF/person = 300 occupants
Step 2: Calculate Required Exit Width (Doors)
300 occupants × 0.15" = 45" total exit width
Step 3: Determine Number of Exits
300 occupants > 49, so minimum 2 exits required
(1-49 = 1 exit, 50-500 = 2 exits, 501-1000 = 3 exits, 1001+ = 4 exits)
(1-49 = 1 exit, 50-500 = 2 exits, 501-1000 = 3 exits, 1001+ = 4 exits)
Step 4: Size Each Exit (50% Rule)
Each exit must handle 50% of load if one is blocked: 45" × 0.5 = 22.5"
But minimum door width is 32", so use two 36" doors (72" total, meets 45" requirement)
But minimum door width is 32", so use two 36" doors (72" total, meets 45" requirement)
Minimum Dimensions (Regardless of Calculation)
32"
Minimum Door Clear Width
Measured with door open 90°
44"
Minimum Corridor Width
When serving 50+ occupants
36"
Minimum Corridor Width
When serving <50 occupants
44"
Minimum Stair Width
Between handrails
11"
Minimum Stair Tread
Tread depth (nosing to nosing)
7"
Maximum Riser Height
4" minimum
Number of Exits Required
1
1-49 occupants
2
50-500 occupants
3
501-1,000 occupants
4
1,001+ occupants
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