Calculators
Lighting Layout Calculator
Calculate the lumens a room needs, the number of fixtures and recessed light spacing from room size and ceiling height.
- Runs in your browser
- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Planning recessed lighting
- Choosing fixture brightness
- Kitchen and office lighting design
- Electrical quotes
About this tool
What the Lighting Layout Calculator does
Lighting is planned in lumens: the target illuminance for the room (in foot-candles or lux) times the floor area, adjusted for how much light reaches the work surface and how fixtures dim over time. A common rule for recessed lights is to space them about half the ceiling height apart.
It also works as a ceiling height lighting calculator or a recessed lighting calculator.
Formula
- Lumens needed = floor area (sq ft) × target foot-candles
- Fixtures = lumens needed ÷ (lumens per fixture × utilisation × light loss factor)
- Recessed spacing ≈ ceiling height ÷ 2
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Room length | 16 ft |
| Room width | 14 ft |
| Ceiling height | 9 ft |
| Target light level | General kitchen (30 fc) |
| Lumens per fixture | 800 |
| Coefficient of utilisation | 60% |
| Light loss factor | 80% |
| Result | Value |
|---|---|
| Fixtures needed | 18 |
| Lumens needed at the surface | 6,720 |
| Suggested spacing between recessed lights | 4.5 |
| Target in lux | 323 |
| Floor area | 224 |
How to read the result
Layer lighting: general light from the calculation, plus task lights over worktops and accent lights for features.
Dimmers let one layout work for both bright tasks and relaxed evenings.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
Work out the lumens the room needs from its area and target light level, then divide by the effective lumens each fixture delivers.
A common rule is about half the ceiling height, so roughly 4 to 4.5 feet apart with a 9 foot ceiling.
One lumen per square foot; about 10.76 lux.
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