How many lumens do I need for a room?

Multiply room square footage by the target foot-candles, then adjust for ceiling height, maintenance and utilization. Divide by lumens per fixture to estimate fixture count.

What is the difference between lux and foot-candles?

Both measure illuminance. One foot-candle equals about 10.7639 lux.

Should I calculate by watts or lumens?

Use lumens when possible. Watts measure energy use, while lumens measure light output. Watt-based estimates are only approximate.

Room Lighting Calculator

Estimate room lighting needs from square footage, target foot-candles or lux, lumens per bulb, ceiling height and maintenance factors.

Room length, ft

Room width, ft

Room type

Lumens per bulb or fixture

Use the actual lumen rating from the bulb package or fixture specification.

Ceiling height

Maintenance factor

Utilization factor

Use this as a planning estimate, not a lighting design, for residential and small-workspace lighting. Final layouts need fixture photometry, beam spread, glare, color rendering, dimming, local code and a qualified lighting design when safety or compliance matters.

Calculate lumens for a room

English room-lighting SERPs expect a practical lumens workflow: room size in square feet, a target lighting level in foot-candles or lux, fixture lumens and a count of bulbs or fixtures.

Lu m e n s = A r e a_{f t^{2}} \times F oo t c an d l es \times F a c t or s

Factors include ceiling height, maintenance and utilization allowances.

1 f oo t c an d l e = 10.7639 l ux

Foot-candles are common in U.S. lighting references; lux is the SI illuminance unit.

Planning limits

Estimate, not a lighting design

Fixture layout, beam angle, glare, color rendering, dimming, task lighting, emergency lighting and local code can all change the final design.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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