Lighting Lumens Calculator — LED bulbs per room
Required lumens by room size and use type. Suggests how many LED bulbs or downlights to install.
Quick answer
Multiply room area in sqm by lux target. Bedroom 100–150 lux, living 200, kitchen 300, office 500. A 150 sqft bedroom (14 sqm × 150 lux = 2,100 lumens) needs about 5 × 5W LED downlights or 2 × 12W bulbs.
Room details
Lighting needed
5bulbs
5W LED downlights for 120 sqft bedroom
Room area120 sqft (11.2 sqm)
Lux target150 lux
Total lumens needed1,673 lm
Per bulb450 lm
Bulbs / fittings5 bulbs
How room lighting is calculated
Room lighting needs are measured in lux — the amount of light falling on a square metre of surface. Multiply the room's area (in sqm) by the recommended lux for that room type to get the total lumens required. Then divide by the lumens output of your chosen bulb to get the count.
Formula: Bulbs = ⌈(Room area in sqm × Lux target) ÷ Bulb lumens⌉
How to use this calculator
- Measure the room length and width in feet (the calculator converts to sqm).
- Pick the room use — bedrooms need warm, low light (100–150 lux); kitchens and offices need much brighter (300–500 lux).
- Pick a bulb type — 5W downlights are common for ceiling installs, 9W bulbs are typical replacements for old incandescent fittings.
Lux targets by room (Indian standards)
| Room | Lux target | Notes |
|---|---|---|
| Bedroom | 100–150 lux | Warmer light (2700K) |
| Living / dining | 200 lux | Mix of ambient + task |
| Kitchen | 300 lux | 500 lux on counters |
| Bathroom | 200 lux | 500 lux at mirror / vanity |
| Office / study | 500 lux | 4000–5000K cool white |
| Workshop | 750–1000 lux | Detail work, drafting |
Tips for layered lighting
- Layer your lighting — combine ambient (overall), task (focused) and accent (decorative) for the best result.
- Add 20% extra for rooms with dark walls or floors — they absorb more light.
- Use dimmers on living and dining lights to let users adjust mood without changing fittings.
Frequently asked questions
How many lumens for a 200 sqft living room?
A 200 sqft living room (about 18.6 sqm) at 200 lux requires roughly 3,720 lumens — equivalent to 4 LED bulbs of 1,000 lumens each, or 8–10 recessed downlights.
What is lux vs lumens?
Lumens measure the total light output of a bulb. Lux measures how much light falls on a surface per square metre. A room's lighting target is set in lux, which you multiply by the room area in sqm to get total lumens needed.
How many LED downlights per room?
A typical 5W LED downlight gives about 400–500 lumens. Divide your total required lumens by 450 to get the count. For a 150 sqft bedroom you'd typically need 4–5 downlights.
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