Free tool
Lux Calculator: How Many Lights Does Your Room Need?
Pick the room, enter its size and the lumens of your fixture. You get the lumens the room needs, how many fixtures to install and the lux you will get, using the same method our lighting designers use.
Download the Excel calculatorSame formulas, room by room. Free, no sign-up.
How the calculation works
- Lumens needed = target lux × room area (length × width).
- Add 30%, because LEDs lose light output as they age (an L70 LED has lost 30% of its output at the end of its rated life).
- Divide by the lumens of one fixture × its loss factor: 0.8 for downlights on a standard ~3 m ceiling, 0.5 for cove lighting that bounces off the ceiling.
- Round up: that is the number of fixtures. Chandeliers, wall lights and decorative pieces are not counted.
Recommended lux levels by room
| Space | Recommended lux | Why | Source |
|---|---|---|---|
| Bedroom | 150 lux | Rest space, low ambient light | IES |
| Living room | 100–150 lux (dimmable to ~50) | General living, adjustable for mood | IES |
| Hallway / corridor | 50 lux | Walking area only | IES |
| Kitchen (counter) | 300–500 lux | Food prep, task lighting | EN 12464-1 / ISO 8995-1 |
| Bathroom (mirror) | 300+ lux | Grooming tasks | IES |
| Home office | 300 lux | Reading and general task work | EN 12464-1 / ISO 8995-1 |
Questions about lux
How do I calculate lux for a room?
Multiply the lux the room needs by its area in square metres to get the lumens needed. Add 30% for LED ageing, then divide by the lumens of one fixture times its loss factor (0.8 for downlights, 0.5 for cove lighting). Round up to get the number of fixtures.
What is the difference between lux and lumens?
Lumens are the amount of light a fixture produces. Lux is how much of that light lands on a surface: 1 lux is 1 lumen per square metre.
How many lux does a bedroom, living room or kitchen need?
About 150 lux for a bedroom, 100–150 lux for a living room (dimmable lower for mood), 300–500 lux on a kitchen counter, 300 lux for a home office and 50 lux for a hallway.
Does colour temperature (Kelvin) change the lux I need?
No. Kelvin describes the colour of the light, from warm to cool white. Lux describes the amount of light. The calculation uses lumens and area; choose the Kelvin separately for the mood of the room.
Why add 30% to the lumens?
LEDs start losing output from the first day. Building in 30% means the room still has enough light when the fixtures have aged, not only when they are new.
Do chandeliers and wall lights count?
No. Chandeliers, wall lights and decorative lighting are for looks. Count only the lights that do the work, usually downlights and cove lighting.
Read the full guide
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