Enter egress design information
Use adopted code values whenever they differ from the included screening presets.
Formula used
Occupant load = floor area ÷ occupant-load factor
Required width = occupant load × capacity factor × (1 + design allowance)
Maximum supported occupants = effective clear width ÷ capacity factor
Effective clear width = measured width − applicable projections and obstructions
The calculator compares the capacity result with the selected dimensional minimum. It then rounds every exit upward using the chosen construction increment.
How to use this calculator
- Select required width or maximum occupant capacity.
- Choose the width units, code preset, and egress component.
- Calculate occupant load by area, manual entry, or floor schedule.
- Select protection, hazard, accessibility, and building conditions.
- Enter the exit count and occupant distribution.
- Enter measured clear widths or calculate door-leaf openings.
- Add obstructions, design allowance, and rounding requirements.
- Review each exit, the bottleneck, and loss scenario.
- Export the results and verify them with the authority.
Example data table
| Scenario | Occupants | Component | Factor | Calculated capacity width | Important comparison |
|---|---|---|---|---|---|
| Business floor | 200 | Door or corridor | 0.20 in/person | 40 in total before allowance | Minimum dimensions can control |
| Assembly level | 600 | Stairway | 0.30 in/person | 180 in total before allowance | Three-exit screening may apply |
| Protected building | 400 | Other component | 0.15 in/person | 60 in total before allowance | Eligibility must be verified |
| Workplace route | 50 | Exit access | User planning factor | Depends on selected factor | OSHA screening minimum is 28 inches |
Exit width planning guidance
Exit width begins with a defensible occupant load. Floor area alone cannot define every real occupancy condition. Fixed seating, stages, equipment, and mixed uses need separate review.
Capacity factors convert occupants into a calculated egress width. Stairways commonly use a larger factor than level components. A dimensional minimum may still exceed the capacity calculation.
Measure clear width at the governing obstruction point. Door stops, hardware, handrails, and inactive leaves can reduce capacity. Nominal product sizes should never replace verified field dimensions.
Multiple exits need realistic occupant distribution assumptions. Equal sharing is convenient but may not reflect actual paths. Remote exits, signage, and space arrangement influence expected usage.
Where routes merge, downstream components may serve combined loads. A corridor can therefore control an otherwise adequate door system. The bottleneck check helps reveal these hidden deficiencies.
Stair calculations need careful story-by-story interpretation. Some paths serve individual floors before merging at discharge. Others accumulate occupants and require broader downstream capacity.
Sprinkler and voice-alarm reductions require exact eligibility. Hazardous and healthcare occupancies often have special limitations. Local amendments can remove or revise model-code exceptions.
Accessible egress involves more than minimum clear width. Areas of refuge and communication systems may be required. Door maneuvering clearances also remain separate design checks.
Existing buildings can follow different compliance pathways. Alterations may trigger upgrades beyond the immediate work area. Document the selected code path before relying on calculations.
A passing result only confirms selected numerical checks. It does not confirm travel distance or exit separation. Fire ratings, discharge, hardware, and illumination still require review.
Use a practical allowance when early dimensions remain uncertain. Rounding upward supports available door and construction sizes. Avoid using safety margins to conceal unreliable occupant assumptions.
Compare each exit rather than only combined total width. One oversized exit cannot always compensate for another deficiency. Individual minimums and distribution rules may govern separately.
The loss scenario is a resilience screening tool. Adopted rules may define a different remaining-capacity threshold. Document why the selected percentage suits the project.
Keep calculations with plans, assumptions, and code references. Future reviewers must understand every input and deduction. Clear documentation prevents silent changes during later design stages.
Final approval belongs to the enforcing jurisdiction. Coordinate early with building and fire officials. Qualified review protects occupants when unusual conditions affect egress.
Reference basis: ICC model-code egress concepts and OSHA 29 CFR 1910.36 workplace exit-route requirements. Verify the locally adopted edition and amendments.
Frequently asked questions
What is exit width?
Exit width is the usable clear dimension available for occupants moving through an egress component. The measurement point depends on the component and adopted code.
Why can the minimum width control?
A small occupant load can produce a narrow capacity result. Codes also establish minimum dimensions for usability, accessibility, emergency movement, and component construction.
Should nominal door width be used?
No. Clear opening width can be smaller than the nominal leaf size because stops, thickness, hardware, mullions, and inactive leaves affect the opening.
How are occupants divided between exits?
The calculator supports equal or custom distribution. Use a defensible distribution based on route arrangement, remoteness, visibility, signage, and applicable code rules.
Can one wide exit offset a narrow exit?
Not always. Individual exit minimums, assigned occupant loads, loss-of-exit rules, and required exit arrangements can prevent simple total-width compensation.
Does a sprinkler system always reduce width?
No. A reduction applies only where the adopted code permits it and every required protection condition is satisfied for the occupancy.
What does the bottleneck result mean?
It identifies the exit with the smallest ratio of effective available width to calculated required width. The full route may contain another controlling component.
Why check decreasing width toward discharge?
A narrowing downstream path can restrict occupants collected from wider upstream components. The entered sequence provides a simple warning for that condition.
Does this calculator approve an egress design?
No. Approval requires the adopted code, complete plans, local amendments, fire-safety coordination, accessibility review, and acceptance by the enforcing authority.