Lumens Per Room Calculator
A 200 square foot room that needs 30 foot-candles takes about 6,000 lumens.
Quick answer: Multiply the area in square feet by the target foot-candles. For example, 200 sq ft at 30 foot-candles is 6,000 lm, 100 sq ft at 15 foot-candles is 1,500 lm and 150 sq ft at 50 foot-candles is 7,500 lm.
The lumens per room formula
Lumens needed equal room area in square feet times the target in foot-candles.
Divide by the lumens of one bulb to count the bulbs.
Take 200 sq ft at 30 foot-candles. 200 × 30 gives 6,000 lm.
Take 100 sq ft at 15 foot-candles. 100 × 15 gives 1,500 lm.
Area times light level
One foot-candle is one lumen on each square foot, so lumens needed equal area times the target level (Home Depot: How to Estimate Lumens for Your Space).
The target depends on what the room is used for.
How to convert lumens per room step by step
- Measure the room area in square feet.
- Pick a target in foot-candles for the room use.
- Multiply the two numbers to get lumens.
- Divide by the lumens of one bulb to count bulbs.
Example 1: 200 sq ft at 30 foot-candles
- Start with 200 sq ft at 30 foot-candles.
- 200 × 30 = 6,000.
- The light needed is 6,000 lm.
200 sq ft at 30 foot-candles = 6,000 lm
Example 2: 100 sq ft at 15 foot-candles
- Start with 100 sq ft at 15 foot-candles.
- 100 × 15 = 1,500.
- The light needed is 1,500 lm.
100 sq ft at 15 foot-candles = 1,500 lm
Example 3: 150 sq ft at 50 foot-candles
- Start with 150 sq ft at 50 foot-candles.
- 150 × 50 = 7,500.
- The light needed is 7,500 lm.
150 sq ft at 50 foot-candles = 7,500 lm
The three examples below use common sizes.
Each one shows the sum in full.
lumens per room conversion table
| Room and target | Lumens needed | Bulbs of 800 lm |
|---|---|---|
| 40 sq ft at 20 foot-candles | 800 lm | 1 bulbs of 800 lm |
| 60 sq ft at 20 foot-candles | 1,200 lm | 1.5 bulbs of 800 lm |
| 80 sq ft at 30 foot-candles | 2,400 lm | 3 bulbs of 800 lm |
| 100 sq ft at 10 foot-candles | 1,000 lm | 1.25 bulbs of 800 lm |
| 100 sq ft at 15 foot-candles | 1,500 lm | 1.875 bulbs of 800 lm |
| 120 sq ft at 40 foot-candles | 4,800 lm | 6 bulbs of 800 lm |
| 150 sq ft at 50 foot-candles | 7,500 lm | 9.375 bulbs of 800 lm |
| 200 sq ft at 15 foot-candles | 3,000 lm | 3.75 bulbs of 800 lm |
| 200 sq ft at 30 foot-candles | 6,000 lm | 7.5 bulbs of 800 lm |
| 250 sq ft at 30 foot-candles | 7,500 lm | 9.375 bulbs of 800 lm |
| 300 sq ft at 20 foot-candles | 6,000 lm | 7.5 bulbs of 800 lm |
| 400 sq ft at 50 foot-candles | 20,000 lm | 25 bulbs of 800 lm |
| 600 sq ft at 30 foot-candles | 18,000 lm | 22.5 bulbs of 800 lm |
The highlighted row is the default of the calculator. The last column gives bulbs of 800 lm.
A quick mental shortcut for lumens per room
For a living room at 15 foot-candles, multiply the square feet by 15. A 200 square foot room needs about 3,000 lumens.
For a kitchen at 35, multiply by 35 instead.
Targets by room
Guides give 10 to 20 foot-candles for living rooms and bedrooms, 30 to 40 for kitchens and dining rooms, and 20 to 50 for bathrooms and offices. Task areas such as a workbench can need 100 or more (Penn State EGEE 102: How Much Lighting Is Needed).
Pick the target that fits how you use the room.
Layers of light
Rooms often mix ambient light and task light. Add the lumens of each layer, and place task lights where you work.
Dimmers let you lower the level when you do not need full light.
Light is lost
Dark walls, shades and dirt reduce the light that reaches the room. Add a margin of 20 percent or more for dark rooms.
Check the bulb data for the lumens at the end of its life.
Quick conversion answers
| Conversion | Result |
|---|---|
| 100 sq ft at 15 foot-candles | 1,500 lm |
| 200 sq ft at 30 foot-candles | 6,000 lm |
| 300 sq ft at 20 foot-candles | 6,000 lm |
| 400 sq ft at 50 foot-candles | 20,000 lm |
Where this conversion is used
Home owners plan lighting for a new room.
Contractors set lumens for a quote.
Common mistakes to avoid
- Using square metres. This page needs square feet.
- Using one target for every room. A kitchen needs more than a bedroom.
- Counting watts. Count lumens.
- Forgetting dark walls. They soak up light.
Related converters
More rooms and targets
50 sq ft at 15 foot-candles is 750 lm. 75 sq ft at 20 foot-candles is 1,500 lm. 90 sq ft at 25 foot-candles is 2,250 lm.
110 sq ft at 30 foot-candles is 3,300 lm. 140 sq ft at 35 foot-candles is 4,900 lm. 180 sq ft at 40 foot-candles is 7,200 lm.
220 sq ft at 25 foot-candles is 5,500 lm. 320 sq ft at 30 foot-candles is 9,600 lm. 500 sq ft at 35 foot-candles is 17,500 lm.
Doubling the first number
100 sq ft at 15 foot-candles is 1,500 lm. 150 sq ft at 20 foot-candles is 3,000 lm. 180 sq ft at 25 foot-candles is 4,500 lm.
220 sq ft at 30 foot-candles is 6,600 lm. 280 sq ft at 35 foot-candles is 9,800 lm. 360 sq ft at 40 foot-candles is 14,400 lm.
440 sq ft at 25 foot-candles is 11,000 lm. 640 sq ft at 30 foot-candles is 19,200 lm. 1,000 sq ft at 35 foot-candles is 35,000 lm.
The same room with different targets
200 sq ft at 10 foot-candles is 2,000 lm. 200 sq ft at 20 foot-candles is 4,000 lm. 200 sq ft at 30 foot-candles is 6,000 lm.
200 sq ft at 50 foot-candles is 10,000 lm.
Frequently asked questions
How many lumens does a room need?
Multiply the area in square feet by the target foot-candles.
How many lumens for a 200 square foot living room?
About 2,000 to 4,000 lumens at 10 to 20 foot-candles.
What is a good foot-candle target for a kitchen?
Guides suggest 30 to 40, with 50 to 100 at task areas.
How many bulbs do I need?
Divide the lumens by the lumens of one bulb and round up.
Do I need extra for dark walls?
Yes, add a margin of 20 percent or more.
Can I use metric?
Use the lux to lumens page with square metres.
Sources
- Home Depot: How to Estimate Lumens for Your Space (homedepot.com)
- Penn State EGEE 102: How Much Lighting Is Needed (courses.ems.psu.edu)
