About the Lux to Lumens Converter
This lux to lumens converter works out how much light output (lumens) you need to reach a target brightness on a surface (lux) over a given area, and does the reverse: how many lux a set of lamps will deliver across a room. Because lux is lumens per square meter, you cannot convert between the two without an area — so the tool asks for the room or surface size in square meters or square feet.
It is aimed at homeowners choosing LED bulbs, electricians and designers doing a quick lighting estimate, photographers and growers checking light levels, and anyone reading a lux meter. Foot-candles (lumens per square foot), common in the US, are shown too, and the chart compares the lumens your area needs for typical room types.
By default the tool assumes all the light lands evenly on the surface. Real rooms lose light to walls, fixtures, dirt and distance, so lighting designers apply a utilization or light-loss factor — set the "light reaching the surface" percentage to 50–70% for a more realistic whole-room estimate.
With the default inputs, the lumens needed is 6,000 lm. Change any value above to recalculate instantly.
How to use the lux to lumens converter
- 1Enter the area of the room or surface and choose m² or ft².
- 2Enter the target illuminance in lux (see the table for typical levels).
- 3Optionally lower "light reaching the surface" to allow for real-room losses.
- 4Read the lumens you need, then compare with your bulbs' lumen ratings.
- 5To check existing lights, enter their total lumens to see the resulting lux.
Formula and method
Lux measures illuminance — light falling on a surface — and is defined as one lumen per square meter. So the lumens needed equal the target lux multiplied by the area in square meters, and the lux produced equals lumens divided by area. A foot-candle is one lumen per square foot, which is 10.764 lux because a square meter is 10.764 ft².
The utilization factor UF (the "light reaching the surface" percentage) accounts for light absorbed by walls, fixtures and distance. At 100% the result is the pure unit conversion; lighting designers typically use 0.5–0.7 for rooms. Areas in square feet are converted with 1 ft² = 0.09290304 m².
- lux
- Illuminance, lumens per square meter
- lm
- Luminous flux (light output), lumens
- UF
- Utilization factor, share of light reaching the surface
- fc
- Foot-candles, lumens per square foot
Worked examples
Kitchen: 20 m² at 300 lux
300 lux × 20 m² = 6,000 lumens. A single 800-lumen bulb spread over the same 20 m² would give only 800 ÷ 20 = 40 lux.
Home office: 150 ft² at 500 lux
150 ft² × 0.0929 = 13.94 m², and 500 × 13.94 = 6,968 lumens. 3,000 lumens over 150 ft² is 3,000 ÷ 150 = 20 foot-candles, or about 215 lux.
Allowing for light loss: 60% utilization
A 10 m² bedroom at 150 lux needs 1,500 lumens on the surface; with only 60% of the light arriving you need 1,500 ÷ 0.6 = 2,500 lumens. 1,600 lumens would deliver 1,600 × 0.6 ÷ 10 = 96 lux.
Frequently asked questions
How do I convert lux to lumens?+
Multiply lux by the illuminated area in square meters. For example, 400 lux over 5 m² needs 400 × 5 = 2,000 lumens. You cannot convert without knowing the area.
How do I convert lumens to lux?+
Divide the lumens by the area in square meters. A 1,000-lumen lamp lighting 4 m² evenly gives 1,000 ÷ 4 = 250 lux (before any losses).
What is the difference between lux and lumens?+
Lumens measure the total light a source emits; lux measures how much of that light lands on each square meter of a surface. The same bulb gives fewer lux over a larger area.
How many lux is a foot-candle?+
One foot-candle equals 10.764 lux, because it is one lumen per square foot and a square meter is 10.764 square feet. To go from lux to foot-candles divide by 10.764.
How many lux do I need in a room?+
Common guidance is about 100–150 lux for hallways and living rooms, 300 lux for kitchens and bathrooms, 500 lux for offices and reading, and 750–1,000 lux for detailed work.