Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Lumen-method average only. Uniformity, glare, room geometry and regulatory lighting requirements are not evaluated.
Example Calculation
- Room area: 20 m²
- Target average illuminance: 300 lux
- Utilization factor: 60 %
- Maintenance factor: 80 %
- Lumens per fixture: 2000 lm
20 m² at 300 lux, utilization 60% and maintenance 80% require 12,500 initial lumens, or seven 2000-lm fixtures.
Frequently asked questions
How do I use this calculator?
Enter room area, target average illuminance, utilization factor, maintenance factor, lumens per fixture. The result updates automatically. Use Reset to restore the example values.
What method does it use?
fixtures=ceil(area × lux /(fixture lumens × utilization × maintenance)).. Lumen-method average only. Uniformity, glare, room geometry and regulatory lighting requirements are not evaluated.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.