Find out how bright a room should be. Pick the room type and enter its size to get the total lumens you need from recommended foot-candle levels, the number of bulbs to buy, and what those bulbs mean in watts.
Last updated:
Units
ft
m
ft
m
fc
1 fc = 10.764 lux
Bulbs
lm
800 lm ≈ 60 W bulb, 1100 ≈ 75 W, 1600 ≈ 100 W
h
Enter your values to see the result.
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How to use the Lumens Calculator
Choose feet or meters and enter the room length and width.
Pick the room type (or enter your own foot-candle target) and how bright you want it within the recommended range.
Enter the lumens per bulb printed on the box, for example 800 lm for a 60 W-equivalent LED.
Read the lumens needed and the number of bulbs or fixtures, then compare the wattage of different bulb types in the table.
The lumens formula
A foot-candle (fc) is one lumen spread over one square foot, so the total light a room needs is simply:
Lumens = floor area (sq ft) × target foot-candles
In metric the same idea uses lux: Lumens = area (m²) × target lux, with 1 fc = 10.764 lux. Divide the result by the lumens printed on your bulb box and round up to get the number of bulbs.
Example: a 12 × 10 ft kitchen is 120 sq ft. At 35 fc it needs 120 × 35 = 4,200 lumens, or six 800-lumen bulbs (4,800 lm).
Recommended foot-candles by room
These residential targets are typical values derived from lighting-design guidance (IES). Use the low end for relaxed spaces and the high end for task lighting or older eyes.
Room
Foot-candles
Lux
Lumens for 100 sq ft
Hallway / stairs
5–10
54–108
500–1,000
Living room
10–20
108–215
1,000–2,000
Bedroom
10–20
108–215
1,000–2,000
Dining room
30–40
323–431
3,000–4,000
Kitchen (general)
30–40
323–431
3,000–4,000
Home office / laundry / garage
30–50
323–538
3,000–5,000
Bathroom vanity, kitchen counters
70–80
753–861
7,000–8,000
Workshop
70–100
753–1,076
7,000–10,000
Watts to lumens
Since LEDs replaced incandescent bulbs, brightness is labeled in lumens. This table shows the usual equivalents.
Lumens
Incandescent
Halogen
CFL
LED
450 lm
40 W
29 W
8–9 W
5–6 W
800 lm
60 W
43 W
13–14 W
8–10 W
1,100 lm
75 W
53 W
18–19 W
11–13 W
1,600 lm
100 W
72 W
23–26 W
15–18 W
2,600 lm
150 W
—
40–42 W
25–28 W
Tip: layer your lighting. Ceiling fixtures can supply the general (ambient) lumens while lamps and under-cabinet lights add the extra task light where you read or cook.
Frequently asked questions
How do I calculate how many lumens I need?
Multiply the floor area in square feet by the recommended foot-candles for the room. One foot-candle is one lumen per square foot, so a 12 × 14 ft living room (168 sq ft) at 15 fc needs about 2,520 lumens. In metric, multiply square meters by lux.
How many lumens per square foot does a room need?
Common residential targets are about 10–20 lumens per sq ft for living rooms and bedrooms, 30–40 for kitchens and dining rooms, 30–50 for home offices and laundry rooms, and 70–80 for bathroom vanities and kitchen counters where you do detailed tasks.
How many lumens is a 60 watt bulb?
A standard 60 W incandescent bulb gives about 800 lumens. Other common equivalents are 40 W ≈ 450 lm, 75 W ≈ 1,100 lm, 100 W ≈ 1,600 lm and 150 W ≈ 2,600 lm. An LED with the same light output uses only about 8–10 watts.
What is the difference between lumens, lux and foot-candles?
Lumens measure the total light a bulb emits. Lux and foot-candles measure how much of that light falls on a surface: 1 lux is 1 lumen per square meter and 1 foot-candle is 1 lumen per square foot, so 1 fc = 10.764 lux.
Should I add extra lumens for high ceilings or dark walls?
Yes. The simple area method assumes a standard 8–9 ft ceiling and fairly light surfaces. Dark walls and floors absorb light and tall ceilings put fixtures farther away, so plan roughly 10–25% more lumens or use dimmable fixtures so you can adjust.
Does the calculator account for light lost by shades and fixtures?
No. It uses the bulb's rated lumens. Frosted shades, deep recessed trims and fixture losses can reduce delivered light, so choose the high end of the range or add a bulb if your fixtures are enclosed.
Is my data sent anywhere?
No. All calculations run in your browser and nothing you enter is uploaded.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.