About this calculator
Number of downlights for a room from the light level it needs, laid out on an even grid with spacing from the walls.
How it’s calculated
Lumens = target lux × floor area. Fittings = lumens ÷ lumens per fitting, rounded up and arranged on a grid that follows the room’s proportions, with the first light half a spacing from each wall. Futurelight, a South African lighting supplier, suggests 100 to 200 lux for lounges and bedrooms and 300 to 500 lux for kitchens and home offices, LED downlights of 500 to 800 lumens, and spacing of about the ceiling height ÷ 2 (1.2 to 1.8 m), at least 0.6 m from the walls.
Worked example
With these inputs:
- Room length
- 5 m
- Room width
- 4 m
- Ceiling height
- 2.4 m
- Room and light level
- Kitchen or home office (300 lux)
- Lumens per fitting
- 700
the result is:
- Downlights
- 9 lights
- Target light level
- 300 lux
- Lumens needed
- 6,000
- Spacing along length
- 1.67 m
- Spacing across width
- 1.33 m
Tips from the trade
- Under-cabinet and task lights are extra. Don’t count them in this figure.
- Choose warm white (2,700 to 3,000 K) for lounges and bedrooms and 4,000 K for kitchens and offices, and keep one colour within a room. Have new lighting circuits installed and certified by a registered electrician.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and SANS 10400 (the National Building Regulations) and your local municipality before ordering.