Estimate room lighting with the lumen method
Learn how illuminance, fixture lumens, room area, and utilization factor combine in a transparent preliminary lighting estimate, then run the bilingual calculator with your own values.
01 / Turn a lighting target into a fixture estimate
Turn a lighting target into a fixture estimate
The lumen method starts with the light level a space should receive and works backward to the total light output. It makes the assumptions visible before you choose a fixture layout or product.
E = (N × F × UF) / A
Required lumens equal target illuminance E multiplied by room area A, divided by the utilization factor UF. The calculator divides required lumens by the output of one fixture and rounds up to a whole preliminary fixture count.
- Illuminance is expressed in lux: one lux is one lumen distributed across one square metre.
- The calculation treats the room as a simple area and applies one utilization factor to account for light reaching the working plane.
- The fixture output is the rated lumen value supplied as an input, before project-specific depreciation or control strategy adjustments.
- The result is preliminary and does not replace a photometric layout, glare review, emergency-lighting check, or code review.
02 / From target lux to a room concept
From target lux to a room concept
- 01
Choose a target illuminance in lux that fits the room use and the standard or brief governing the project.
- 02
Multiply the target by floor area to find the useful light required at the working plane.
- 03
Adjust for utilization, divide by the lumen output per fixture, and round up to a whole fixture count.
- 04
Review spacing, mounting height, glare, controls, maintenance, and local requirements before final specification.
03 / Lighting questions worth checking early
Lighting questions worth checking early
These answers clarify the terms behind the estimate and show where a complete lighting design adds detail beyond a simple lumen-method check.
04 / Continue with the engineering calculators
Continue with the engineering calculators
Run the lighting estimate with your own room values, or use the related tools to check the surrounding engineering quantities in one place.
Estimate fixture count and achieved illuminance for an early room check.
Lighting levelEstimate a preliminary round or rectangular duct size from airflow inputs.
Duct sizingEstimate straight-pipe friction loss with visible assumptions.
Pipe pressure dropConvert length, area, pressure, temperature, and flow values consistently.
Unit converter