Room Lighting Calculator
Total lumens and number of luminaires needed to reach a target illuminance.
Results
Luminous flux
12,500
lm
Lamps needed
9
Luminous flux
6000
lm
What this tool does
Not all the light a lamp emits reaches the working plane: some is absorbed by walls and ceiling, and output falls as fixtures age and collect dust. The utilisation and maintenance factors account for both. Common targets are 150 lux for a corridor, 300 for a living room and 500 for office or workshop tasks.
Formula
lumens = lux × area ÷ (utilisation factor × maintenance factor)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
a | Area | m² |
lx | Target illuminance | lx |
uf | Efficiency | % |
mf | Percentage | % |
ll | Lumens per lamp | lm |
LM | Luminous flux | lm |
N | Lamps needed | — |
LA | Luminous flux | lm |
Worked example
- Area20 m²
- Target illuminance300 lx
- Efficiency60 %
- Percentage80 %
- Lumens per lamp1500 lm
- Luminous flux12,500 lm
- Lamps needed9
- Luminous flux6000 lm
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.