How many lumens does a room need?
Multiply the floor area by the room's footcandle target: 10 to 20 for living rooms and bedrooms, 20 to 50 for bathrooms and offices, 30 to 40 for kitchens and dining rooms. A 12 by 15 ft living room needs about 2,700 delivered lumens, so plan roughly 3,900 rated lumens, about five 800 lumen bulbs.
Updated · By the Interior Redesign AI editorial team · Sources cited on the page
The 0.7 allowance is our assumption for light lost to shades, fixtures and walls. Use 1 for bare bulbs in a white room, 0.5 for dark shades or high ceilings.
Lumens to install
3,860 lm
5 bulbs of 800 lm for 180 sq ft at 15 fc.
| Floor area | 180 sq ft |
|---|---|
| Target (living room) | 15 fc |
| Lumens reaching the room | 2,700 lm |
| Rated lumens (÷ 0.7) | 3,857 lm |
| Range for this room type | 2,571-5,143 lm |
| Bulbs | 5 × 800 lm |
Ambient light only. Add task light at desks, mirrors and reading chairs. Room targets are IES residential levels as published by Penn State.
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Key numbers
- 1 footcandle
- 1 lumen per sq ft = 10.764 lux (NIST)
- Living room, bedroom
- 10-20 fc ambient (IES, via Penn State)
- Kitchen, dining room
- 30-40 fc general (IES, via Penn State)
- Bathroom, home office
- 20-50 fc (IES, via Penn State)
- Hallway, entry
- 5-20 fc (IES, via Penn State)
- 60 W bulb replacement
- About 800 lumens (FTC)
- Light-loss allowance
- Divide by 0.7 (our assumption): buy about 43% more than the delivered lumens
Worked example
A 12 × 15 ft living room
Ambient light at the middle of the living room range (15 fc), the default 0.7 light-loss allowance, 800 lumen bulbs.
- Area: 12 × 15 = 180 sq ft.
- Delivered: 180 × 15 fc = 2,700 lumens.
- Rated: 2,700 ÷ 0.7 = 3,857 lumens (range 2,571-5,143 for 10-20 fc).
- Bulbs: 3,857 ÷ 800 = 4.8, rounded up to 5.
Plan about 3,900 rated lumens: 5 bulbs of 800 lumens, ideally on a dimmer.
How we calculate
A footcandle is one lumen spread over one square foot (NIST lists both as 10.764 lux), so delivered lumens = floor area × footcandles. The footcandle ranges per room are the IES residential levels published on Penn State's EGEE 102 course page. We start at the middle of each range; you can change it.
Not every rated lumen reaches the floor: fixtures, shades, ceiling height and dust absorb some. The lumen method in lighting design multiplies rated lumens by a coefficient of utilization and a light-loss factor. We use a combined 0.7 by default. That is our planning assumption, not a measured value, and the widget lets you change it from 0.5 (dark shades, high ceilings) to 1 (bare bulbs, white room).
Bulb count divides the rated lumens by the lumens per bulb on the package. The default of 800 lumens is the FTC's figure for a bulb that replaces a 60 W incandescent.
Estimates, sources
Planning estimates and published guidelines, not quotes, designs or code rulings. Figures were checked on each source on the date shown. Local prices, your home and your jurisdiction's adopted code decide the real answer.
- How Much Lighting is Needed (EGEE 102), IES residential levels (Penn State College of Earth and Mineral Sciences, as of Oct 26, 2026): attributed to IES: living rooms, bedrooms 10-20 fc (ambient); kitchen general 30-40 fc; bathrooms 20-50 fc; home office/reading 20-50 fc; dining room 30-40 fc; hallways and entryways 5-20 fc; garage general 30 fc
- NIST Guide to the SI, Appendix B.9: conversion factors (National Institute of Standards and Technology (NIST), as of Oct 26, 2026): footcandle and lumen per square foot: both 1.076391 E+01 lux (10.76391 lx)
- A Practical Guide to Indoor Office Lighting (the lumen method) (EC&M, 2002): illuminance = fixtures × lamp lumens × coefficient of utilization × light-loss factor ÷ area; the 0.7 combined factor is our assumption
- Shopping for Light Bulbs (Federal Trade Commission (FTC) Consumer Advice, as of Oct 26, 2026): a traditional 60-watt incandescent bulb produces about 800 lumens; an LED can produce the same 800 lumens using about 9 watts
Lumens per square foot by room
Footcandles are lumens per square foot, so these are also delivered lumens per square foot. Rated lumens to buy, at our 0.7 allowance, are in the last column. A small 40 sq ft bathroom at 35 fc needs about 2,000 rated lumens.
| Room | Footcandles (lm per sq ft) | Rated lm per sq ft to buy |
|---|---|---|
| Living room | 10-20 | 14-29 |
| Bedroom | 10-20 | 14-29 |
| Kitchen (general) | 30-40 | 43-57 |
| Dining room | 30-40 | 43-57 |
| Bathroom | 20-50 | 29-71 |
| Home office or reading | 20-50 | 29-71 |
| Hallway or entry | 5-20 | 7-29 |
| Garage (general) | 30 | 43 |
Spread the lumens over layers
The total is for ambient light across the room. Reading chairs, desks, vanities and counters want more on the task itself: Penn State's page gives about 50 fc for reading and writing at home. Add a lamp or task light there instead of brightening the whole room.
For a kitchen, use the kitchen lighting calculator, which adds task light for counters and islands and spaces recessed lights by ceiling height.
How to use this tool
Pick the room
Each room type sets a footcandle range from the IES levels.
Enter the size
Length and width of the floor, in feet or meters.
Adjust if needed
Change the footcandles, the light-loss allowance or the lumens per bulb.
Read the lumens
Delivered lumens, rated lumens to buy and the bulb count.
Questions
How many lumens do I need for a living room?
About 10 to 20 lumens per square foot reaching the room, or 14 to 29 rated lumens per square foot at our 0.7 allowance. A 12 × 15 ft room needs roughly 2,600 to 5,100 rated lumens.
How many lumens for a bedroom?
The same 10 to 20 footcandles as a living room for ambient light, plus a reading lamp. A 12 × 12 ft bedroom needs about 1,440 to 2,880 delivered lumens.
How many lumens does a bathroom need?
20 to 50 footcandles. A 5 × 8 ft bathroom needs about 800 to 2,000 delivered lumens, with the brightest light at the mirror.
What is the difference between lumens and footcandles?
Lumens measure the light a bulb gives off. Footcandles measure the light landing on a surface: one lumen per square foot.
Why do you add extra lumens?
Shades, fixtures, dark walls and dust absorb light, so the floor gets less than the bulbs' rating. Dividing by 0.7 is our planning assumption; change it to match your fixtures.
How many lumens is a 60 watt bulb?
About 800 lumens, according to the FTC. An LED can give the same 800 lumens on about 9 watts.
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