How to use the room lighting calculator
- Enter the room length and width.
- Choose the type of room.
- Enter the lumens per bulb from the packaging. 800 lm is a common output for a standard LED bulb.
The calculator uses the midpoint of a published range for each room and shows the range alongside. Reach the total with several fixtures rather than one bright ceiling light. Decoratoradvice finds layered light easier to live with.
Light levels by room
From Penn State's EGEE 102 course, citing Illuminating Engineering Society (IES) guidance for homes:
| Room | Range (foot-candles) | Midpoint used |
|---|---|---|
| Living room, bedroom | 10–20 | 15 |
| Kitchen (general) | 30–40 | 35 |
| Dining room | 30–40 | 35 |
| Bathroom | 20–50 | 35 |
| Home office or reading area | 20–50 | 35 |
| Hallway or entry | 5–20 | 12.5 |
Kitchen task areas over the stove and sink are listed at 50–100 foot-candles, which is usually provided by under-cabinet or pendant lights on top of general lighting.
The formula
Lumens = room area (sq ft) × foot-candles
Bulbs = lumens ÷ lumens per bulb, rounded up
Lux = foot-candles × 10.764
Worked examples
A 14 × 12 ft living room:
168 sq ft × 15 = 2,520 lumens
2,520 ÷ 800 = 3.15, so 4 bulbs
A 10 × 10 ft home office:
100 sq ft × 35 = 3,500 lumens
3,500 ÷ 800 = 4.4, so 5 bulbs
Tips
- Treat the result as a starting point. Dark walls and floors absorb light; light colours reflect it. If you are repainting, the paint calculator covers the walls.
- Layer the light: ambient light from this calculation, task lights for work areas, and accent lights for features.
- Use dimmers so one layout works for bright tasks and quiet evenings.
- Estimate running costs from the bulbs' wattage with the electricity cost calculator.
Common mistakes
- Counting watts instead of lumens. LED wattage is much lower than older bulbs for the same light.
- Lighting only the middle of the room. Spread fixtures so corners are not dark.
- Using ambient levels for tasks. Reading and cooking need extra light where you work.
Frequently asked questions
How many lumens do I need for a living room?
At 10–20 foot-candles, a 168 sq ft room needs about 1,680–3,360 lumens; the midpoint is 2,520.
What is a foot-candle?
One lumen spread over one square foot. One foot-candle is about 10.76 lux.
How many lumens is a 60 W equivalent LED?
Packaging for 60 W-equivalent LED bulbs commonly lists about 800 lumens. Check the box.
How bright should a kitchen be?
The published range for general kitchen lighting is 30–40 foot-candles, with 50–100 at the stove and sink.
How do I measure an L-shaped room?
Add the areas of each part with the square footage calculator, then enter the total as length × 1.
Key takeaways
- Lumens = area in sq ft × foot-candles.
- Ranges by room come from IES-based guidance; the calculator uses the midpoint.
- Add task lighting on top of general lighting.
- Compare bulbs by lumens, not watts.