Recessed Lighting Calculator

Recessed cans get planned two ways, and this tool does both. The layout mode takes the room size and ceiling height and returns the number of fixtures, the spacing between centres and how far the first row sits off the wall, using the rule that spacing runs at about half the ceiling height. The brightness mode takes the room size, what the room is used for and the lumens printed on the box, and returns how many fixtures reach the light level that job usually wants. Fixture and electrician prices are yours to enter, since there is no built-in price list, and new circuits, switches, ceiling patching and permits are left out of the total.

Calculator Type
Measured In
Applies to every measurement on this form and to the answers. The layout is all ratios of lengths, so the unit cancels through it; what follows the choice is the floor area, the density and the light level.

Room size and ceiling height in, a grid of cans out. Leave the spacing at zero to use half the ceiling height.

Leave at zero and half the ceiling height is used, which is the usual starting rule. A zero here means the rule, so it is left as zero in both units.
Housing and trim, or the price of an all-in-one LED can. Leave at zero to skip the costing.
What an electrician charges to cut in and wire one light. Leave at zero for a materials-only figure.
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Measured In
Applies to every measurement on this form and to the answers. The layout is all ratios of lengths, so the unit cancels through it; what follows the choice is the floor area, the density and the light level.

Pick what the room is for and the output of the fixture you are buying.

A footcandle is a lumen per square foot of floor and a lux is a lumen per square metre, so the figure used follows the unit above. The two columns are each market's own specified level rather than a conversion: 20 fc is 215 lux, but metric practice writes 200, the same way US practice writes 20 and not 18.6.
Off the box. A 6 inch LED can is often 650 to 1,100 lumens. A lumen is a lumen in both systems, so this box never changes.
Housing and trim, or the price of an all-in-one LED can. Leave at zero to skip the costing.
What an electrician charges to cut in and wire one light. Leave at zero for a materials-only figure.
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