Recessed lighting is an unobtrusive way to add illumination or highlighting to an area, but it is easy to under- or overestimate how many lights are needed in a certain space. That’s where lighting estimation comes in. By estimating your lighting needs, you can determine the number and spacing of fixtures required to give you perfect illumination.
Lighting an Area
Measure the size of the space that you intend to light. Multiply the width by the depth to obtain the square footage of the area.
Multiply the square footage of the area by 1.5, which is the number of watts per square foot that the average residential space requires. This gives you the total required wattage for the space.
Determine the type of bulb that you plan to use: A typical recessed light uses a 65-watt incandescent bulb. Divide the required wattage number that you calculated previously by the wattage of the bulbs that you are using. This gives you the number of fixtures to be used in the space.
Divide the number of fixtures around the space evenly, leaving equal space around the perimeter and at least 2 feet between the fixtures and the wall. Because this method is a general estimation, you can add or remove or a fixture or two to achieve symmetry in the room.
Highlighting a Surface
Measure the length of the item that you want to highlight. For a wall area, measure the area that you want illuminated, and for a bookcase, desk or other surface, measure from one end of the item to the other. Measure the depth of the item if applicable to obtain the square footage of the surface.
Calculate lighting needs using the same process of determining lighting for an area to decide how many recessed lights to mount in the space. Multiply the square footage by 1.5 and divide that number by the wattage of the fixture you intend to use.
Measure the height to the ceiling in which the lighting will be installed if the surface sits near a wall. Divide that height by 4 to determine how far away from the wall the lights must sit to highlight the surface without creating harsh lighting on the wall. For instance, an 8-foot wall would require lights to be mounted 2 feet out from the wall.
Things You Will Need
- Measuring tape
- Always use at least two recessed lights, even if the calculation calls for only one, and choose bulbs with lower wattage instead.
- Lighting Design Basics; Mark Karlen and James Benya
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