How to choose LED potlight wattage and beam angle

Two questions come up on nearly every potlight order: how many watts, and how far apart. Neither has a single answer, but both have a method.

Stop specifying by wattage

Wattage measures what a fixture consumes, not what it produces. A 9W LED slim panel puts out roughly the same light as an old 65W incandescent can, and two 12W fixtures from different manufacturers can differ by 200 lumens. Specify lumens and treat wattage as the number that matters for the circuit, not the room.

Rough output ranges for the sizes we stock most:

• 3.5 inch — 8–12W, roughly 600–900 lumens. Hallways, closets, tight soffits.
• 4 inch — 9–12W, roughly 750–1,000 lumens. The general-purpose residential size.
• 6 inch — 12–15W, roughly 1,000–1,300 lumens. Living areas, higher ceilings, wider spacing.

How many fixtures

Start from the room, not the fixture. A usable rule for general residential lighting is 20 lumens per square foot for living areas and 40–50 for kitchens and workshops, then divide by the output of one fixture.

A 12 × 14 ft kitchen is 168 sq ft. At 40 lumens per square foot that is 6,720 lumens, or about seven 4-inch fixtures at 1,000 lumens each. Round to the layout, not the arithmetic — an even six or eight will look better than a lopsided seven.

Spacing

The common starting point is ceiling height divided by two. An 8 ft ceiling gives 4 ft between fixtures; a 9 ft ceiling gives 4.5 ft. Keep the first row 2–3 ft off the wall, or 1.5–2 ft if you are deliberately washing a wall or cabinet run.

Spacing tighter than this does not usually improve the room — it raises cost and creates a spotted ceiling. Spacing wider leaves scallops of shadow between fixtures.

Beam angle

Beam angle decides whether light lands where you want it. Most residential LED panels are fixed at a wide 100–120°, which is what you want for general ceiling coverage. Narrower optics concentrate light and are worth specifying when the ceiling is high or the target is small.

• 100–120° — general ambient light, standard 8–9 ft ceilings.
• 60–90° — higher ceilings, or where you want defined pools of light.
• Adjustable gimbal — sloped ceilings, artwork, wall washing, anything you need to aim after the fact.

On a sloped ceiling a fixed downlight throws its beam perpendicular to the slope rather than at the floor. That is what gimbal potlights exist for — the Votatec 4-inch gimbal slim pot light and the Liteline LUNA round gimbal both aim after installation.

Two things that catch people out

Cut-out size is not fixture size. A "4 inch" potlight does not necessarily fit a 4 inch hole. Check the manufacturer's cut-out dimension before you drill, especially when replacing another brand.

Fire-rated assemblies need fire-rated fixtures. If the ceiling forms part of a rated assembly, the fixture has to maintain that rating. Our fire-rated potlights are listed for it; a standard slim panel is not, whatever else it has going for it.

What to order

For most residential work a 4-inch slim panel like the Votatec 9W 5CCT slim panel covers the job, with 6-inch panels in larger rooms. Browse the full range in LED potlights and downlights or recessed lighting.

Check before you install. This guide summarises common practice to help you specify parts. The Ontario Building Code, the Ontario Fire Code and the Canadian Electrical Code are the authority, they are revised periodically, and your local authority having jurisdiction can be stricter. Confirm current requirements and have the work done by a licensed electrician.