Lighting
Lighting Lumens Calculator
Work out how many lumens a room needs. Enter the floor area and room type, and we calculate the total lumens for balanced light, plus an LED wattage estimate to shop with.
Last updated: June 2026
How lighting levels are calculated
Lighting engineers measure illuminance in lux (lm/m²). Different tasks require different lux levels: a bedroom needs only 100 lux for a relaxed atmosphere, while a home office requires 300–500 lux for comfortable work.
Formula used
Total lumens = floor area (m²) × recommended lux × ceiling height factor
Ceiling height factor = ceiling height / 250 cm
LED wattage = total lumens / 90 lm/W
Number of 800 lm bulbs = ceil(total lumens / 800)
Worked examples
Kitchen 12 m², 300 cm ceiling: 12 × 300 × 1.2 = 4,320 lm → 48 W LED → 6 × 800 lm bulbs.
Bedroom 16 m², 250 cm ceiling: 16 × 100 × 1.0 = 1,600 lm → 18 W LED → 2 × 800 lm.
Home office 10 m², 270 cm ceiling: 10 × 400 × 1.08 = 4,320 lm → 48 W LED.
How to use this calculator
- Measure floor area (length × width).
- Select the room's primary use — this sets the lux target.
- Enter ceiling height. Standard is 240–260 cm.
- Spread fittings evenly to avoid dark corners.
Recommended lux by room type
| Room | Lux | Atmosphere |
|---|---|---|
| Bedroom | 100 | Relaxed, warm |
| Living room | 150 | Comfortable general |
| Hallway | 100 | Safe navigation |
| Dining room | 200 | Social, flattering |
| Bathroom | 250 | Clear grooming |
| Kitchen | 300 | Task-ready |
| Home office | 400 | Focus, eye comfort |
Notes & limitations
This calculator gives general ambient totals. Task lighting should be added separately. Perceived brightness depends heavily on wall and ceiling reflectance.
Frequently Asked Questions
How many lumens do I need for a 20 m² living room?
A living room needs approximately 150 lux. For 20 m²: 20 × 150 = 3,000 lumens minimum. Add 10–20% for fitting losses: 3,300–3,600 lumens. Four 800-lumen LED bulbs achieves this.
What is lux and how does it differ from lumens?
Lumens measure the total light output of a source. Lux measures how much of that light falls on a surface: 1 lux = 1 lumen per square metre.
How many lumens does a kitchen need?
Kitchens require 300–500 lux. For a 12 m² kitchen at 300 lux: 12 × 300 = 3,600 lumens. Add task lighting under cabinets.
Does ceiling height affect how many lumens I need?
Yes. Light intensity falls with distance. A fitting at 3 m delivers less lux to the floor than the same fitting at 2.4 m. Our calculator applies a height correction factor.
How many watts is 3000 lumens in LED?
Modern LED bulbs produce approximately 80–100 lumens per watt. At 90 lm/W, 3,000 lumens ≈ 33 watts of LED — equivalent to a 200-watt incandescent bulb.