YepCalc

Recessed Lighting Calculator

Find how many recessed lights a room needs and where to put them. Enter the room and the ceiling height to see the grid of lights, the spacing between them, and the distance from the walls. It works the same for can lights, pot lights, and downlights. To find how many lumens the room needs, use the Lumens Calculator.

Section 1

Add another rectangle for an L-shaped room, or use Quantity for identical rooms.

Spacing

From the floor to the ceiling.

Center to center between lights. Leave blank to use half the ceiling height.

From each wall to the centers of the nearest lights. Leave blank to use half the spacing between lights.

Cost

Result

Enter the length and width of the room to see the lights you need.

How to lay out recessed lights

The calculator places the lights in a grid of rows and columns, with the same spacing along each wall. Along the length of the room, and again along the width, it splits the wall into equal parts no longer than the max spacing, and puts a light in the middle of each part:

Lights along the length = length ÷ max spacing, rounded up

Spacing = length ÷ lights along the length

Distance from the walls = spacing ÷ 2

The lights along the width are found the same way, and the room gets lights along the length × lights along the width. Each light then lights the same size of floor. The count is rounded up, not to the nearest number, so the lights are never farther apart than the max spacing. The spacing is measured between the centers of the lights, and the distance from the walls to the center of the nearest light.

When you enter a wall distance

If you enter a Wall distance, the outer lights go that far from the walls, and the space between them is split the same way:

Lights along the length = (length − 2 × wall distance) ÷ max spacing, rounded up, + 1

Spacing = (length − 2 × wall distance) ÷ (lights along the length − 1)

In a narrow room, two rows at the wall distance would sit half the max spacing apart or closer. When a side (the length or the width) is 2 × wall distance + half the max spacing or less, the calculator puts one row down the center of that side instead. For a 4 ft 6 in hallway with a 2 ft wall distance and 4 ft max spacing, two rows would be only 6 in apart, so you get one row, 2 ft 3 in from each wall. A wall distance of 0 puts the centers of the outer lights on the walls.

Spacing

If you leave Max spacing blank, the calculator uses half the ceiling height, such as 4 ft for an 8 ft ceiling. That's the rule of thumb in the Philips Hue FAQ How far should recessed lights be from the wall? and in 1000Bulbs' Recessed Specs for Success: divide the ceiling height by two.

It's on the close side. Eaton's Spacing guide for recessed LED lighting says each light has a spacing criterion, usually 0.5 to 1.5, and the spacing criterion × the ceiling height is the most the lights should be apart. Half the ceiling height matches the smallest of these, so it gives the most lights. Other guides space them wider: Steven Bliss's Best Practices Guide to Residential Construction gives 6 to 7 1/2 ft for an 8 ft ceiling, and ERCO's guide to arranging luminaires up to 1.5 times the light's height above the work surface. If the spec sheet for your light gives a spacing criterion, multiply it by the ceiling height and enter that as the Max spacing.

Distance from the walls

If you leave Wall distance blank, the lights sit half the spacing from the walls, as ERCO and Bliss recommend. Some guides use a set distance instead: 1000Bulbs suggests about 3 ft from the walls to cut down shadows in the corners. For lighting a wall (wall washing), Philips Hue gives 1.5 to 2 ft (50 to 60 cm) from the wall, and 12 to 18 in (30 to 45 cm) in front of cabinets. Those layouts follow the wall or the counter, not a grid, so the calculator doesn't place them.

L-shaped rooms

Each rectangle gets its own grid, and the line between two rectangles is treated like a wall. The lights on either side of it are the two wall distances apart. With Wall distance blank, that's half of each rectangle's spacing added together, so it's no more than the max spacing. To leave out part of a room, enter the rest as rectangles.

Cost

The cost is the number of lights × the price per light. If the lights come in a box of 4 or 12, divide the box price by the number in the box and enter that.

Examples

A 12 × 12 ft room with an 8 ft ceiling

The max spacing is 96 ÷ 2 = 48 in. Each wall is 144 in, and 144 ÷ 48 = 3, so you need 3 × 3 = 9 lights, 4 ft apart and 2 ft from the walls.

A 13 × 12 ft room

Along the 13 ft length, 156 ÷ 48 = 3.25 rounds up to 4 lights, 156 ÷ 4 = 39 in apart (3 ft 3 in) and 19 1/2 in from the walls. Along the width you get 3 lights 4 ft apart, as above, so you need 4 × 3 = 12 lights. With a 2 ft wall distance, it's still 12 lights, 3 ft apart along the length.

A hallway

A 10 × 3 ft hallway takes one row of 3 lights down the center, 3 ft 4 in apart and 1 ft 8 in from the ends.

A Metric room

A 5 × 4 m room with a 2.4 m ceiling has a max spacing of 1.2 m. That's 5 ÷ 1.2 = 4.17, rounded up to 5 lights, and 4 ÷ 1.2 = 3.33, rounded up to 4, so you need 20 lights, 1 m apart and 500 mm from the walls.

FAQ