π‘ Lighting Calculator
Find how many lumens your room needs and how many bulbs that means.
Bulbs Needed
How to Use This Calculator
Lighting design starts with one question: how much light does this room need? This calculator answers it in lumens, then converts that into a bulb count you can shop with.
Select the room type. Each room has a recommended foot-candle range based on what you do in it.
Enter the room length and width in feet. The calculator multiplies them to get square footage.
Enter the lumens per bulb from the bulb packaging. A standard 60 watt equivalent LED is 800 lumens; a 100 watt equivalent is about 1,600.
Optionally enter the ceiling height to get a recessed light spacing estimate.
Read the total lumens, the bulb count (rounded up), and the fixture suggestions for that room type.
Foot-Candles: How Bright Each Room Should Be
A foot-candle is simply one lumen landing on each square foot, so multiplying room area by the target foot-candles gives the total lumens the room needs. Relaxing rooms want low numbers, working rooms want high numbers. This calculator uses the midpoint of each range, which suits most homes; go toward the high end if the room has dark walls or few windows.
Worked Example
A 12x14 ft kitchen: 12 x 14 = 168 sq ft. Kitchen general lighting targets the midpoint of 30 to 40 foot-candles, which is 35. Total lumens = 168 x 35 = 5,880. With 800 lumen bulbs (standard 60 watt equivalent LEDs), bulbs needed = 5,880 / 800 = 7.35, rounded up to 8 bulbs. Those 8 bulbs cover general light; add under-cabinet strips or pendants over the counters for the 70 to 80 foot-candle task lighting that kitchens really run on.
Fixture and Layout Tips
Total lumens only matter if they land where you need them. Spread bulbs across the room instead of relying on one bright central fixture: several medium sources beat one harsh one. For recessed lights, space them about half the ceiling height apart (4 ft on an 8 ft ceiling) in an even grid, then add task lights where work happens. Put living rooms, bedrooms, and dining rooms on dimmers so one lighting plan covers movie night and homework alike. Match color temperature within each room: 2700K for cozy spaces, 3000K to 4000K for kitchens, baths, and offices. And remember that dark paint, dark floors, and heavy window coverings all absorb light, so rooms with those finishes should aim for the high end of their foot-candle range.
Frequently Asked Questions
What is a lumen vs a watt?
A lumen measures how much light a bulb actually produces; a watt measures how much electricity it uses. Old incandescent bulbs tied the two together, so people shopped by watts. LEDs broke that link: a 60 watt equivalent LED uses about 9 watts but still puts out 800 lumens. When you buy bulbs now, shop by lumens for brightness and check watts only for energy use.
How many lumens per square foot for a kitchen?
Plan on 30 to 40 lumens per square foot for general kitchen lighting, which is 30 to 40 foot-candles. Task areas like counters and the stove want 70 to 80 lumens per square foot, usually from under-cabinet lights or pendants. A 12x14 ft kitchen (168 sq ft) needs about 5,880 lumens of general light plus dedicated task lighting over work surfaces.
How many recessed lights do I need?
A common rule is to space recessed lights about half the ceiling height apart: on an 8 ft ceiling, roughly 4 ft apart in a grid. Divide the room area by the square of that spacing for a rough count. A 168 sq ft kitchen at 4 ft spacing needs about 10 to 11 cans. That is a layout guide, not a law: dimmers let you tune the result, and task areas need their own lights regardless of the grid.
What color temperature should I choose?
Use 2700K (warm white) in living rooms and bedrooms where you want a cozy feel, 3000K to 3500K in kitchens and hallways for a clean neutral light, and 3500K to 4000K in bathrooms and home offices where you need to see detail. Keep every bulb in one room at the same temperature: mixing 2700K and 5000K in one space looks accidental and harsh.
Do lumens add up?
Yes. Lumens are additive: two 800 lumen bulbs in one room deliver 1,600 lumens of total light, minus small losses to shades and fixture direction. That is why this calculator divides total lumens needed by lumens per bulb to get the bulb count. The one catch is distribution: 8,000 lumens from one corner fixture lights a room worse than 8,000 lumens spread across several fixtures, so spread the bulbs around.