General Lighting Calculator
Estimate how many lights you need for ambient (general) lighting in any room. Works for recessed cans, surface mounts, or any fixture.
How to Use
- Measure your room’s length and width (in feet).
- Enter ceiling height (affects spacing recommendation).
- Set desired foot‑candles based on room function (see hints).
- Enter lumens per light from your fixture packaging.
- Click “Calculate” to see the minimum number of lights needed and approximate spacing.
Example
Scenario: 15 ft x 12 ft living room (180 ft²), 9 ft ceiling, want 30 fc, using 800‑lumen LED downlights.
Calculation: Total lumens needed = 180 × 30 = 5400 lm → lights = ceil(5400/800) = 7. Spacing ≈ √(180/7) ≈ 5.1 ft between lights. Keep 2–3 ft from walls.
What is General Lighting?
General (or ambient) lighting provides overall illumination for a room. It’s the base layer of light that allows you to move around safely and see the space. This calculator uses the lumen method: multiply room area by desired foot‑candles to get total lumens, then divide by lumens per light. The result gives you the minimum number of fixtures needed.
For even distribution, place lights in a grid pattern with spacing roughly equal to the square root of (area / number of lights). Taller ceilings may allow wider spacing because light spreads more. Always consult a lighting professional for final design.