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Source verifiedIBC 2024 model codeCapacity only

Egress Capacity
Calculator

Calculates capacity-based width from occupant load and component type. It does not determine the final required stair, corridor, door, or ramp dimension.

Who it's for: architects checking the capacity-based egress width for a stair, door, corridor, or ramp once occupant load and sprinkler condition for that component are known, at construction documents or permit review.

Scope boundary
Reduced factors require a qualifying sprinkler system and emergency voice/alarm communication. They are not available for Groups H or I-2. Component-specific minimums, local amendments, and unimplemented exceptions remain separate checks.

How to use this calculator

1
Enter the occupant load served
Use the occupant load served by the specific component, not the whole building.
2
Choose the component, occupancy group, and sprinkler/alarm condition
Select stairway, door, corridor, or ramp; the occupancy group; and whether a qualifying sprinkler system and emergency voice/alarm communication are present.
3
Read the required capacity-based width
The result is the required capacity-based width in inches for that component. Check it next against the component's own prescriptive minimum dimension — this page reports capacity only.

The formula

Required capacity width = occupant load served × capacity factor (IBC 2024 §§1005.3.1–1005.3.2, unamended model code). Stairways: 0.3 inch per occupant, reduced to 0.2 where the building has a qualifying sprinkler system (§903.3.1.1 or §903.3.1.2) and emergency voice/alarm communication, except Groups H and I-2. Other egress components (doors, corridors, ramps): 0.2 inch per occupant, reduced to 0.15 under the same conditions.

Worked example

Example
A stairway serving 200 occupants in an unsprinklered Group B building: 200 occupants × 0.3 in/occupant (§1005.3.1, no qualifying sprinkler system) = 60 in required capacity-based width.

When this estimate will be off

  • Returns capacity-based width only. Minimum component dimensions, distribution of egress width, loss of an exit, accessibility, local adoption and amendments, and complete compliance are separate checks.
  • The reduced 0.2/0.15 factor is not available for Groups H and I-2, regardless of sprinkler or alarm condition.
  • The reduced factor requires both a qualifying sprinkler system and the required emergency voice/alarm communication together, not either alone.

Frequently asked questions

A common mistake: Returns capacity-based width only. Minimum component dimensions, distribution of egress width, loss of an exit, accessibility, local adoption and amendments, and complete compliance are separate checks.

IBC 2024 §§1005.3.1–1005.3.2 exclude Groups H and I-2 from the sprinkler-based reduction regardless of sprinkler or alarm condition, so this calculator does not apply it to those groups.

Yes. The reduced factor requires both a qualifying sprinkler system (§903.3.1.1 or §903.3.1.2) and the required emergency voice/alarm communication together, not either alone.

No. This is the capacity-based width only. The component's own minimum dimension, egress-width distribution, and loss-of-an-exit provisions are separate checks not evaluated here.

Sources and review record

Sources and method basis

Limitations

  • Returns capacity-based width only; component minimums, distribution, loss of an exit, local adoption, amendments, and complete compliance are separate checks.

This free IBC 2024 Egress Capacity Calculator is built and maintained by DataDrivenAEC, using the relevant codes and standards. It does not substitute for professional judgment.