The standard rule is to space recessed lights at a distance equal to half the ceiling height. For an 8-ft ceiling, space fixtures 4 ft apart. For a 9-ft ceiling, use 4.5 ft spacing. The first row of lights should be placed half that spacing distance from the wall — so 2 ft from the wall for an 8-ft ceiling. This provides even illumination without hot spots or dark zones.

For a 12 × 12 ft bedroom (144 sq ft) at 15 foot-candles with 800-lumen 6" fixtures, you need approximately 4–6 fixtures arranged in a 2 × 2 or 2 × 3 grid. For a kitchen at the same size requiring 50 foot-candles, you would need 12–14 fixtures. Room type and desired brightness level are the primary factors.

A foot-candle (FC) is a measure of illuminance — the amount of light falling on a surface. One foot-candle equals one lumen per square foot. Typical recommendations: hallways 10 FC, bedrooms 15–20 FC, living rooms 20–30 FC, offices 50 FC, kitchens 50 FC at counter level, and bathrooms 70 FC for grooming tasks. Task areas like kitchen counters may need supplemental under-cabinet lighting in addition to recessed fixtures.

4" recessed fixtures (typically 600–700 lumens) work well in smaller rooms, hallways, bathrooms, and as accent lighting. 6" fixtures (800–1,100 lumens) are the most common choice for general lighting in living rooms, kitchens, and bedrooms. In rooms with ceilings taller than 10 ft, consider 6" high-output fixtures or commercial-style 8" cans to ensure adequate light reaches the floor level.