Lumens Calculator

The short answer

The U.S. Department of Energy’s guide gives 10 to 20 lumens per square foot for bedrooms and living areas, and 75 to 80 for kitchens and bathrooms. Multiply by the room’s square feet: a 120 sq ft living room needs 1,200 to 2,400 lumens, or 2 to 3 bulbs of 800 lumens (the old 60-watt kind).

Tasks need more light where you work: the IES table gives 20 foot-candles (220 lux) on a desk and 50 foot-candles (540 lux) on a kitchen prep counter. A lamp close to the task gives that without lighting the whole room to the same level.

How to use the calculator

1. Pick the room and enter its length and width.
2. Pick the bulbs your lamps will take. The lumens are printed on the box and on the base of most LED bulbs.
3. Add the lights already there. If the room has a ceiling fixture or other light that stays, add up its bulbs’ lumens. The calculator takes them off the total.

The result shows the room’s total in lumens, how many bulbs of your size that takes, the light levels for the room’s tasks and the color temperature to look for. Use Copy link to keep the numbers when you shop for lamps.

Lumens by room size

What a room needs in all, from the Department of Energy’s lumens per square foot:

HUD’s inspection standard for assisted housing asks for a permanently installed light in the kitchen and the bathroom, but lets a bedroom or living room have outlets instead of a ceiling light. In many rentals, plug-in lamps provide most of a room’s light: spread the total over the lamps around the room.

Light for tasks

IES, the Illuminating Engineering Society, publishes recommended light levels. Its residential table gives the light that should land on each surface, in foot-candles (lumens per square foot of the surface) and lux:

The reading levels come from the VA’s lighting design manual, which recommends table and floor lamps for rooms meant to feel like home. ENERGY STAR’s specification required certified desk lamps to give at least 200 lumens.

Watts to lumens

LED bulbs are sold by lumens. The FTC’s equivalents for the old incandescent bulbs:

How we calculate

1. Area. The room’s length times its width, in square feet.
2. The room’s light. The area times the Department of Energy’s lumens per square foot: 10 to 20 for bedrooms and living areas, which we also use for dining rooms, home offices and hallways, and 75 to 80 for kitchens and bathrooms. The guide is from DOE’s weatherization program (2024).
3. Lights already there. Their lumens come off the total, and the result says when the room already has enough.
4. Bulbs. What’s left, divided by your bulb’s lumens and rounded up to whole bulbs.
5. Tasks. IES’s residential light levels (The Lighting Handbook, 10th edition, as the Department of Energy reproduced it in 2012), and the VA’s level for reading. They’re light on the surface, so they don’t add to the room’s total: they tell you where to aim a lamp.
6. Color. The Department of Energy’s color temperature ranges for the two kinds of room, with ENERGY STAR’s names for them.

The two sources measure different things. The lumens per square foot count the light bulbs give off, while IES’s foot-candles count the light that reaches a surface, after some is absorbed by walls, shades and furniture. That’s why a room’s lumens are much higher than its foot-candles would suggest. Dark walls and furniture take more light, as the Department of Energy and GSA note, so aim for the top of the range in a dark room.

Worked examples

Example: A 12 × 10 ft living room with only plug-in lamps

What we know

• Living room, 12 ft by 10 ft (120 sq ft)
• Bulbs: 800 lumens (60 W equivalent)

How it works out

1. DOE's guide for bedrooms and living areas is 10 to 20 lumens per square foot. For 120 sq ft, that's 1,200 to 2,400 lumens.
2. Use 2 to 3 bulbs of 800 lumens (60 W equivalent), spread over as many lamps as suit the room.
3. For tasks, the VA's lighting manual gives 40 foot-candles (430 lux) for reading: light landing on the surface, from a lamp or light close to it, on top of the room's total.
4. Color: DOE's guide gives 2,200 to 3,000 K for bedrooms and living areas, the warm white ENERGY STAR calls ideal for most indoor uses.

1,200 to 2,400 lumens in all: add 2 to 3 bulbs of 800 lumens.

Example: An 11 × 12 ft bedroom with a ceiling light

What we know

• Bedroom, 11 ft by 12 ft (132 sq ft)
• Bulbs: 800 lumens (60 W equivalent)
• Lights already there: 800 lumens

How it works out

1. DOE's guide for bedrooms and living areas is 10 to 20 lumens per square foot. For 132 sq ft, that's 1,320 to 2,640 lumens.
2. With the 800 lumens already there, add 520 to 1,840 lumens: 1 to 3 bulbs of 800 lumens (60 W equivalent).
3. For tasks, IES gives 5 foot-candles (50 lux) for dressing, and the VA's lighting manual gives 40 foot-candles (430 lux) for reading in bed: light landing on the surface, from a lamp or light close to it, on top of the room's total.
4. Color: DOE's guide gives 2,200 to 3,000 K for bedrooms and living areas, the warm white ENERGY STAR calls ideal for most indoor uses.

1,320 to 2,640 lumens in all: add 1 to 3 bulbs of 800 lumens.

Example: A 10 × 7 ft galley kitchen with a ceiling fixture

What we know

• Kitchen, 10 ft by 7 ft (70 sq ft)
• Bulbs: 1,600 lumens (100 W equivalent)
• Lights already there: 1,600 lumens

How it works out

1. DOE's guide for kitchens and bathrooms is 75 to 80 lumens per square foot. For 70 sq ft, that's 5,250 to 5,600 lumens.
2. With the 1,600 lumens already there, add 3,650 to 4,000 lumens: 3 bulbs of 1,600 lumens (100 W equivalent).
3. For tasks, IES gives 50 foot-candles (540 lux) on the prep counter, 30 (320 lux) at the sink and 30 (320 lux) on the cooktop: light landing on the surface, from a lamp or light close to it, on top of the room's total.
4. Color: DOE's guide gives 2,700 to 5,000 K for kitchens and bathrooms; ENERGY STAR calls neutral and cool white good for kitchens and work spaces.

5,250 to 5,600 lumens in all: add 3 bulbs of 1,600 lumens.

Lighting a rental without wiring

• Layer the light. The Department of Energy and GSA describe three layers: ambient light for the room, task light where you work, and accent light. Plug-in floor lamps cover the first, and desk, table and clip lamps the second. The floor lamp guide compares bright LED lamps, lamps you can aim and shade lamps for a corner.
• Use what’s there. Swap the bulbs in the ceiling fixture for brighter LEDs that fit it before you add lamps, and keep the old bulbs to put back when you move.
• Hang a plug-in pendant where a lamp can’t go. A swag pendant over the table or the reading chair plugs into the wall; the pendant light height calculator gives its hanging height and the cord to buy.
• Take it with you. Lamps and bulbs move to your next place, so they count as an upgrade you keep. The upgrade cost calculator shows what that means per month of your lease.