Lumens Calculator
Find how many lumens a room needs, and convert old bulb watts to LED watts.
About the Lumens Calculator
Lumens measure light output; watts measure power used. LEDs give about 80–120 lumens per watt, compared with about 13 for old incandescent bulbs, so a 60 W incandescent equals roughly an 8–9 W LED (800 lumens).
Lux is lumens per square metre falling on a surface. Recommended levels range from about 100 lux in hallways to 500 lux for kitchen worktops and desks (in line with EN 12464-1 office guidance).
The formula
Lumens = lux × area (m²); LED watts ≈ lumens ÷ 100
Incandescent to lumens (US DOE / Energy Star)
| Incandescent | Lumens | Typical LED |
|---|---|---|
| 40 W | 450 | 5–6 W |
| 60 W | 800 | 8–10 W |
| 75 W | 1100 | 11–14 W |
| 100 W | 1600 | 16–20 W |
| 150 W | 2600 | 26–33 W |
Worked example
Example: Lumens needed = 4,088
- Inputs: I want to: Light a room; Room: Living room (200 lux); Floor area: 220; Area in: ft²; New bulb type: LED.
- Formula: Lumens = lux × area (m²); LED watts ≈ lumens ÷ 100
- Result: Lumens needed = 4,088
Questions people ask
How many lumens for a bedroom?
About 150 lux; a 12 m² room needs around 1,800 lm.
Lux vs lumens?
Lumens are total light from a bulb; lux is how much lands on each square metre.