Emergency Lighting Calculator

Calculate emergency fixture spacing, battery runtime, and code compliance for means-of-egress lighting per NFPA 101, IBC, and IES. Minimum 1 fc average, 0.1 fc minimum at floor level.

Corridor / Egress Path

Corridor Length 100 ft

Corridor Width 8 ft

Ceiling Height 9 ft

Fixture Type

Fixture Wattage 10 W

Battery Backup

Battery Capacity 6 Ah

Battery Voltage 12 V

Battery Efficiency 85%

Code Compliance Results

Egress path area—

Required: ≥ 1 fc average—

Required: ≥ 0.1 fc minimum—

Max spacing (1.5× MH rule)—

Fixtures needed—

Actual spacing—

Total emergency load—

Battery runtime—

NFPA 101 requires ≥ 90 min—

—

fixtures

Count needed

—

ft spacing

Along egress

—

minutes

Battery runtime

—

fc avg

Illuminance

Code Reference Summary

Requirement	Standard	Value	Status

Designing emergency lighting

Emergency lighting keeps egress paths visible if normal power fails, and it’s governed by life-safety codes (such as NFPA 101 and local building code). The common requirement is a minimum illuminance along the path of egress — frequently about 1 foot-candle (roughly 10 lux) average at the floor, not dropping below a set minimum, for a required duration (often 90 minutes). Fixtures run from batteries or a central backup supply and must illuminate corridors, stairs, level changes, and exit doors, with illuminated exit signs marking the route. Space units so there are no dark gaps and the path stays continuously lit, and always design to the specific code edition for your building, since exact levels, durations, and testing rules vary.

The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.