How to use this calculator
- Enter Room length in ft.
- Enter Room width in ft.
- Enter Ceiling height in ft.
- Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.
Formula & constants
Spacing rule: ceiling height × 0.5–0.75 = distance between cans; half that to walls. A 12×16 room with 8 ft ceilings takes 6–8 four-inch LED cans on a rough 4–6 ft grid. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.
Aim for ~1.5 W of LED (≈150 lumens) per sq ft in living spaces; kitchens want double.
Where this fits in the project
Electrical sizing works backwards from load: total demand sets service size, circuit amperage sets wire gauge, and conductor count sets conduit fill. HVAC equipment is sized from the BTU load, never from floor area alone.
How this connects to your project
No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the recessed lighting calculator:
- Wire Size Calculator — Lighting circuits require specific wire gauge.
- Electrical Load Calculator — Lighting adds to total electrical load.
- Conduit Fill Calculator — Lighting wiring may run through conduit.
- Paint Calculator — Recessed lights are installed in painted ceilings.
- Drywall Calculator — Recessed lights require holes in drywall ceiling.
Frequently asked questions
How far apart should recessed lights be?
Half to three-quarters of ceiling height between cans — 4–6 ft under an 8 ft ceiling — and half that from walls.
How many lumens per square foot?
General living: 150–200 lm/sq ft (10–20 lumens per sq ft ambient minimum); kitchens and tasks: 300+.
Last verified: — prices reflect current national averages. See our methodology.
Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.