Lux to Lumens Converter
| Room | Target | 20 m² needs |
|---|---|---|
| Living room | 150 lux | 3,000 lm |
| Bedroom | 100 lux | 2,000 lm |
| Kitchen counter | 400 lux | 8,000 lm |
| Office desk | 500 lux | 10,000 lm |
| Hallway | 100 lux | 2,000 lm |
| Bathroom mirror | 400 lux | 8,000 lm |
Lumens and lux measure different things, and the bridge between them is your floor: lumens are the total light a fixture emits, lux is how many of those lumens land on each square meter - so lumens = lux x area in square meters. A 3,000-lumen setup over 20 square meters delivers 150 lux everywhere under it, which is comfortable living-room light. Set any two of the three values and the converter computes the third.
This is the calculation bulb shopping actually needs, because fixture boxes sell lumens while comfort is decided by lux. The targets the lighting industry designs to: 100-150 lux for living rooms and bedrooms, 300-400 for kitchens and bathrooms, 500 for desks and workshops - and for scale, an overcast noon lands about 1,000 lux outdoors while full sun passes 50,000. The table prices the common rooms at 20 square meters so the intuition starts with real furniture.
How to use
- Enter your room area in square meters, then either the target lux or the lumens your fixture list - the third value computes instantly.
- Pick a target from the table: 150 lux is living-room comfortable, 400-500 lux is where kitchens, desks and workshops land.
- Buying bulbs? Add up the lumens on the boxes; judging a room's brightness? That number divided by area is the lux you will feel.
Frequently asked questions
What is the difference between lux and lumens?
Lumens count the light a source gives off in total; lux counts how much of it arrives on one square meter. The same 800-lumen bulb is bright in a closet (high lux) and feeble across a warehouse (low lux), because lux divides the lumens by area. Lumens belong to the fixture, lux belongs to the surface - the converter moves between them through your room size.
How many lumens do I need for a room?
Multiply the room's square meters by the target lux: a 20 m² living room at 150 lux wants about 3,000 lumens total, a 10 m² home office at 500 lux wants 5,000 concentrated on the work surface. Multiple fixtures add their lumens, so four 800-lumen bulbs make 3,200 - the converter above checks any combination against its room.
Why do bulb boxes say lumens instead of watts?
Watts measure electricity drawn, not light delivered - LEDs destroyed that shortcut. A 60-watt incandescent and a 9-watt LED both emit about 800 lumens, so modern boxes lead with lumens and list the watt-equivalent in fine print. Thinking in lumens (then dividing by your area for lux) is the only way to compare a bulb with a strip with a panel honestly.
How bright is daylight in lux?
An overcast noon runs about 1,000-10,000 lux, full daylight 10,000-25,000, and direct sun past 50,000 up to 100,000 lux. That is why a window makes any lamp look weak at noon and heroic at night - indoor targets of 150-500 lux are for evenings and interior rooms, and nobody competes with the sun on its own terms.
Is more lux always better?
No - each task has a comfortable band. Reading wants 300-500 lux, a living room feels relaxing at 100-200, and past about 1,000 lux indoors most people find it clinical (why dentists aim 10,000+ only at one tooth). Age matters too: a 70-year-old eye needs roughly triple the lux of a 20-year-old for the same task, which is why kitchen lighting that suited the parents frustrates the kids.