Case 1
- Luminous flux (lm)
- 800lm
- Lit area (m²)
- 10m²
80.00lx
Open with these valuesLumens to Lux Calculator
80.00lx
Result: 80.00 lxLux is lumens per square metre, so divide the flux by the lit area: 800 lumens over 10 m² is 80 lux, a corridor level, while the same lamp over 4 m² gives 200 lux. The figure is an average — the spot under the lamp is brighter, the corners darker.
Worked examples
Case 2
- Luminous flux (lm)
- 1000lm
- Lit area (m²)
- 4m²
250.00lx
Open with these valuesCase 3
- Luminous flux (lm)
- 500lm
- Lit area (m²)
- 1m²
500.00lx
Open with these valuesHow it's calculated
lux = lumens ÷ area in m²
- StepRead the rated lumens from the lamp packaging, not its wattage.
- StepMeasure the floor or work surface the light has to cover, in m².
- ResultDivide; the result is the average illuminance in lux.
Reference table
| Lumens, area | What that looks like | Lux |
|---|---|---|
| 300, 12 | A dim hallway | 25.00 |
| 800, 10 | One 60 W-equivalent bulb in a small room | 80.00 |
| 1000, 4 | A reading corner | 250.00 |
| 2000, 5 | A kitchen worktop | 400.00 |
| 5000, 10 | An office lit to standard | 500.00 |
Questions
How do I convert lumens to lux?
Divide the luminous flux in lumens by the area in square metres. 800 lumens spread over 10 m² gives 80 lux, a typical corridor level; the same 800 lumens over 4 m² yield 200 lux, suitable for reading.
What is the difference between lumens and lux?
Lumens measure the total light output of a source — the brightness of the bulb itself, regardless of how the light is spread. Lux measure illuminance, how much of that light actually lands on a surface per square metre. The same 1000-lumen bulb creates 1000 lx on one square metre but only 100 lx spread across ten.
What lux level do I need for different rooms?
Corridors and stairwells need about 100 lx for safe navigation, living rooms 150–300 lx, kitchens and offices 300–500 lx. Detailed work such as craft, drawing or technical inspection wants 750–1000 lx or more. These are averages — a lamp above a desk can exceed the room average.
Why does lux go down in a bigger room with the same bulb?
Because illuminance is lumens per square metre. Adding floor area while keeping the lumens constant spreads the same light further and lowers the lux proportionally. To hold the same level in a larger room you need proportionally more lumens.
Does the distance from the bulb affect lux?
Yes, but this calculator uses the total area rather than distance, so it gives an average and not a point measurement. In reality illuminance falls with the square of the distance from the source. For a single point at a known distance use the inverse square law calculator instead.
Sources and last check
Information, not professional advice.