How to plan lighting for a room
Measure the room's length and width, and the height of the ceiling. Then think about what the room is for. A kitchen needs more light than a dining room, because you are working with knives under it. That is why we start with the room type and not with a single figure for the whole house.
Read the lumens on the box of the fixture you like, and ignore the watts. Lumens are the light. Watts are only what it costs to run, and an LED gives out far more lumens per watt than the bulbs those old rules were written for.
Then walk the room for what gets in the way. Ceiling joists decide where a recessed light can go, and a ceiling fan or the door of a tall cabinet can block one completely. Lay the plan on the floor with tape and stand in it before you cut any holes.
A worked example
A vendor guide prints this one: a 12 by 14 foot bedroom at 20 foot-candles. These lines come from the same formula the calculator above runs, and use 800 lumen fixtures as an example.
14 by 12 ft bedroom, 800 lumen fixtures
- Area: 14 × 12 = 168 sq ft
- Low end: 168 × 20 = 3,360 lumens
- High end: 168 × 50 = 8,400 lumens
- Fixtures: 5 to 11
- By spacing at 8 ÷ 2 = 4 ft: 12 lights
The two methods give different answers, which is normal. Spacing has nothing to do with brightness, and it aims for even coverage. Lumens decide how bright it feels. If they disagree, choose lower-output fixtures to fit the spacing, or a dimmer. For what they will cost to run, see the light bulb savings calculator, and dark walls eat light, so a repaint with the paint calculator can do as much as another fixture.
Lumens for common rooms
Ranges are wide because the published guidance is wide. We use one vendor's summary, and others differ, so treat these as starting points and not as a standard.
| Room | Target | Low | High | 800 lumen fixtures |
|---|---|---|---|---|
| Living room, 16 × 14 | 10 to 20 | 2,240 | 4,480 | 3 to 6 |
| Bedroom, 12 × 12 | 20 to 50 | 2,880 | 7,200 | 4 to 9 |
| Kitchen, 12 × 10 | 20 to 50 | 2,400 | 6,000 | 3 to 8 |
| Dining room, 12 × 10 | 10 to 20 | 1,200 | 2,400 | 2 to 3 |
| Bathroom, 8 × 6 | 20 to 50 | 960 | 2,400 | 2 to 3 |
| Hallway, 12 × 4 | 5 to 10 | 240 | 480 | 1 to 1 |
Mistakes that make a room feel wrong
- Buying by watts. Two bulbs of the same wattage can differ widely in brightness. Read the lumens.
- One target for everything. Light on a counter where you chop is a separate job from the general light in the room.
- Lights too near the wall. Retailers warn this casts harsh shadows. A half space from the wall is one common layout.
- Forgetting the fan. A light directly above fan blades flickers as they turn.
- Treating it as code. None of these figures is a code requirement. Wiring, box fill and insulation-contact ratings are questions for a licensed electrician, and are not covered here.
Questions
How many lumens do I need for a living room?
A living room needs about 10 to 20 lumens per square foot, by the vendor table we use. A 200 square foot room is 2,000 to 4,000 lumens. That is general light, and most living rooms also have lamps for reading.
How far apart should recessed lights be?
Space them about half the ceiling height apart, so 4 feet on an 8 foot ceiling and 5 feet on a 10 foot one. That is a rule of thumb from home centers, and a fixture with a wide beam can go further. Check the maker's photometric data.
How many can lights in a 12x12 room?
About 9 by spacing, in 3 rows of 3 on an 8 foot ceiling. By lumens it may be far fewer: a bedroom takes 2,880 to 7,200 lumens, which is 4 to 9 fixtures at 800 lumens each. Use the lumen count to judge brightness.
How do I calculate the lighting for a room?
Multiply the floor area by the target foot-candles to get lumens, then divide by the lumens from one fixture. A 12 by 14 foot bedroom at 20 foot-candles is 168 times 20, which is 3,360 lumens. Round up the fixture count.
What is the difference between a lumen and a foot-candle?
A lumen is the light a fixture gives out, and a foot-candle is how much reaches a surface: one lumen per square foot. Lux is the metric version, and one foot-candle is 10.764 lux.
Do watts tell me how bright a bulb is?
No, watts are how much power a bulb uses. Lumens are how bright it is, and an LED makes far more lumens per watt than an old bulb did. The light bulb savings calculator covers the running cost.
These lumens are a rule of thumb from a vendor's summary of lighting levels and not an IES table or a code requirement. Beam spread, trim, dark walls and dimming all change how bright a room feels. Check the fixture manufacturer's photometric data, and have an electrician handle wiring and insulation-contact ratings.
Sources and review
- Home lighting guide: residential recommended lighting levels, Super Bright LEDs, updated 2026.
- Recessed lighting calculator, Omni Calculator, no date shown, read November 2026.
Checked in November 2026. Spotted a wrong number? Report it and it goes in the corrections log.
How this is calculated
Every figure below is read from the code that produces the answer, so what is written here is what the calculator ran. The constants were last checked against their sources in November 2026.
The arithmetic
Lumens
Lumens = Floor area × Foot-candles
- Foot-candles
- The light level to aim for, low and high
Worked through: 168 × 20 = 3360 lumens
Recessed light spacing
Spacing = Ceiling height ÷ 2
- 2
- A common retailer rule, not a standard
Worked through: 8 ÷ 2 = 4 ft
The constants, and where they come from
FOOT_CANDLES
Modelled from published dataLight levels to aim for, low and high, by room, in foot-candles
- living
- 10, 20
- bedroom
- 20, 50
- kitchen
- 20, 50
- kitchenTask
- 50, 100
- dining
- 10, 20
- bathroom
- 20, 50
- hallway
- 5, 10
- laundry
- 20, 100
- workshop
- 20, 75
Applies to: General home lighting. It is not a code requirement
Source: Home lighting guide: residential recommended lighting levels, Super Bright LEDs, published 2026-08, read 2026-11.
A vendor's table, which says it follows lighting experts including IES without naming a publication. IES's documents are not freely readable, and other vendors differ widely, so we show a range and do not claim it as IES's.
SPACING_DIVISOR
ModelledWhat the ceiling height is divided by to space recessed lights
Applies to: Typical recessed lights on a flat ceiling
No published figure exists for this. It is derived, and the derivation is below rather than a citation to something that does not say it. Last checked in November 2026.
A rule of thumb that Home Depot and Lowe's both give, an 8 foot ceiling meaning 4 foot spacing. We saw those only in search excerpts, as both refused direct requests. It has nothing to do with lumens, so it can disagree with the lumen count.
What the labels mean
- Modelled from published data:
- derived rather than measured, calibrated against the source named beside it.
- Modelled:
- derived rather than measured, and the derivation is shown.
If a figure here looks wrong, it may be. Tell us what you found and we will check it against the source and publish a correction if it needs one. How constants are chosen and how often they are reviewed is set out in our methodology.
How to use the lumens calculator for a room
- 1
Choose the room
- 2
Enter its length, width and ceiling height
- 3
Enter the lumens on the fixture's box
- 4
Read the lumen range and the fixtures that takes
- 5
Compare with the spacing layout, and let the lumen count have the last word on brightness
What this calculator assumes
Every estimate here rests on the assumptions below. Where your job differs from one of them, the figure will differ too.
- Lumens are the floor area times a target, which treats all the light as reaching the floor. Real rooms lose some
- Targets are a range, so you see a low and a high result and not one number
- Spacing at half the ceiling height is a retailer's rule, and it can disagree with the lumen count, so both are shown
- It covers general lighting, not task lights under cabinets or over a desk
Pro tips
- Put the lights on a dimmer, which makes a high count forgiving
- Lay the plan out on the floor in tape and check for fans and joists
- Add task light over a counter or a desk separately