Lighting Lumens Calculator
Lumens and bulbs needed for any room from IES levels.
What it does
Room lighting multiplies floor area by a footcandle target for the room use: living rooms sip at 15, bedrooms take 35, kitchens 40, counters far more. Lumens then divide into bulb counts for shopping.
The tool above takes floor area with room type in imperial or metric. It returns total lumens with an 800 lumen bulb count and the target used beside them.
The default 168 ft² bedroom at 35 footcandles needs 5,880 lumens: 8 bulbs at 800 lm each. A 100 ft² living room at 15 needs 1,500 lumens, just 2 bulbs.
Targets follow Illuminating Engineering Society residential ranges with Energy Star lighting guidance behind efficient choices. Both treat these as general light; counters and desks need dedicated task layers.
How to use
- Pick imperial or metric for the floor area.
- Enter the room floor area.
- Pick the room type for its target.
- Read lumens first for the total.
- Buy the bulb count, then add task lights.
Formula
- footcandles
- Lumens per ft² for the room use.
- 800
- Lumens of a 60 W equivalent bulb.
- round up
- Whole bulbs sold, never fractions.
Metric areas convert to ft² first (x 10.7639), then run one table, so systems agree. Dark walls and high ceilings drink light beyond the plan number.
Worked example
Example: 168 ft² bedroom
Imperial defaults: 168 ft², bedroom 35 fc.
- Lumens: 168 x 35 = 5,880 lm.
- Bulbs: 5,880 / 800 = 7.35, round up to 8.
- Target line reads 35 fc.
- Check: 8 x 800 = 6,400 lm covers the plan.
- Tool shows 5,880 lm, 8 bulbs, 35 fc target.
Reference table
| Room | Footcandles | 168 ft² needs |
|---|---|---|
| Living room | 15 | 2,520 lm |
| Bedroom | 35 | 5,880 lm |
| Kitchen | 40 | 6,720 lm |
| Hallway | 8 | 1,344 lm |
Limits
- General light only; task layers separate.
- Bulb count assumes 800 lm each.
- Ceiling height and colors shift real needs.
- Dimmer compatibility needs checking per bulb.
Common mistakes
- Lighting counters with room general light alone.
- Counting bulb watts instead of lumens.
- Forgetting dark paint absorbs light.
- One central fixture for shadowed corners.
- Skipping dimmers where moods change.
Try it yourself
Quick checks. Answers sit tucked under each question.
100 ft² living room?
100 x 15 = 1,500 lm, 2 bulbs.
200 ft² kitchen?
200 x 40 = 8,000 lm, 10 bulbs.
Bulbs for 5,880 lm?
5880 / 800 = 7.35, so 8 bulbs.
Questions
How many lumens per room?
Area times target: 168 ft² bedroom at 35 fc needs 5,880 lm.
What is a footcandle?
One lumen per square foot of surface light.
How many bulbs is that?
Divide by bulb lumens and round up: 5,880 / 800 = 8 bulbs.
Kitchen brighter?
Yes at 40 general with 50 to 100 on counters as task light.
Watts or lumens?
Lumens measure light; watts measure power. Shop lumens.
What color temperature?
Warm 2700K living areas, neutral 3500-4000K work zones.