Recessed Lighting Calculator
For a standard 8-foot ceiling, space recessed lights 4 feet apart, with the first light 2 feet from each wall. A 12×15-foot room typically needs 6 recessed lights for general lighting, or 8–10 for kitchen task lighting. The core formula: spacing between lights equals ceiling height ÷ 2, and distance from the wall equals half that spacing. Use the calculator below for your exact room dimensions and lighting needs.
Your room
Enter dimensions and lighting purpose. Values convert live between units.
General ambient — even illumination throughout the room (~15 fc).
Advanced options
Larger fixtures cast wider light. 4″ and 6″ are most common.
Brightness per light. Standard LED can lights are 600–800 lumens.
You need
6recessed lights
Spaced 4 ft apart, 2 ft from each wall.
(Spacing: 1.22 m · Wall offset: 0.61 m)
Show how we calculated this
Recessed lights
Room (top-down)
Calculations based on industry-standard spacing formulas from the American Lighting Association and IESNA (Illuminating Engineering Society) guidelines.
Recessed lighting FAQ
Quick answers to the most common recessed lighting layout questions.
How far apart should recessed lights be?
Ceiling height divided by 2. An 8-foot ceiling calls for 4-foot spacing; a 10-foot ceiling calls for 5-foot spacing. This rule keeps overlap even so you avoid bright hotspots and dark valleys across the room.
How far from the wall should the first recessed light be?
Half the spacing distance — so 2 feet for a standard 8-foot ceiling. This puts the first ring of light exactly where the wall meets the floor area you actually use. Closer than 1.5 feet creates wall scallops; farther leaves the perimeter dim.
How many recessed lights do I need for a 12×12 room?
About 6–9 lights for general lighting on a standard 8-foot ceiling. Using 4-foot spacing and a 2-foot wall offset, a 12×12 room fits a 3×3 grid (9 lights). Drop to a 2×3 layout (6) for softer ambient lighting in bedrooms or living rooms.
What size recessed light should I choose — 4-inch or 6-inch?
4-inch for accent and task; 6-inch for general ambient. 4″ fixtures throw a tighter beam and look cleaner in modern rooms. 6″ fixtures spread light wider, so you can use fewer of them in living rooms and basements. 3″ and 5″ are specialty sizes.
How many lumens do I need per recessed light?
600–800 lumens per fixture for general use. Task areas like kitchen counters want 700–1000 lumens per light. Accent fixtures over artwork or fireplaces can drop to 400–500 lumens. Add a dimmer regardless — it lets one layout serve multiple moods.
Can I use recessed lights on a vaulted or sloped ceiling?
Yes — use sloped-ceiling housings and calculate spacing from the average ceiling height. For a ceiling that goes from 8 to 14 feet, plan around 11 feet (5.5-foot spacing). Standard recessed housings will angle the light incorrectly on a slope, so always specify sloped-rated trims.
How do I plan recessed lights over a kitchen island?
Use 2–3 lights spaced 24–30 inches apart, centered over the island. Place them 18–24 inches in from each end. For task lighting, choose 700–900 lumen fixtures with a 35–40° beam angle so light covers the work surface without spilling onto the floor.
Is it possible to have too many recessed lights?
Yes — over-lighting creates an office-like glare and Swiss-cheese ceilings. If a room calculates to more than ~12 fixtures, look at higher-lumen bulbs on dimmers, a mix of recessed plus pendants, or wider spacing. Total room lumens matter more than fixture count.