If you've ever stepped into a home aglow with recessed lighting, you probably couldn't help but be struck by the feeling that someone truly cared about creating a warm atmosphere. Effectively spacing recessed lights is one part art, one part science, one part personal preference and one part patience. In other words, you should be prepared to tweak the spacing plan and make adjustments. While the entire process isn't difficult, it is recursive. But when your eyes light up at the sight of your own well-lit home, you will know that it was worth every minute.
Create a layout of the room on plain or graph paper. Mark the dimensions of the room as well as the placement and size of furniture. Work with a No. 2 pencil and keep an eraser nearby.
Calculate how much wattage your room will need -- the first step in determining how many recessed lights you should buy and then where to place them. Multiply the width of the room by the length in feet; then multiply this number by 1.5. So if your family room is 20 feet wide by 20 feet long, you will need 600 watts of light because 20 x 20 = 400 x 1.5 = 600.
Determine how many recessed lights you will need by first deciding how bright you wish each light to be. Most recessed fixtures can accommodate 75- or 100-watt bulbs, but you might wish to err on the side of caution and select 60-watt bulbs so that the lights do not resemble spotlights. Divide the total wattage needed in the room by the bulb size. So in this example, 600 divided by 60 equals 10, meaning that you will need 10 lights to amply light the room. Alternatively, you might wish to err on the side of "overlighting" the room and installing dimmer switches on the recessed lights. So if you decide to use 100-watt bulbs, you would need only six lights because 600 divided by 100 equals six.
Remain flexible at this point in the process, remembering that these formulas are meant to guide your efforts, not mandate them. In the end, you might wish to add or subtract a light or two. For example, you might decide to disregard formulas and spacing in the interest of highlighting a focal point in the room, such as a fireplace or a prized family portrait.
Space the first four lights by starting at the corners of the room and measuring 3 feet in. This distance will help ensure that the recessed lights do not create shadows in the corners, thereby making the room appear smaller than it is. With the first four lights tentatively placed, go about evenly spacing the remaining lights, leaving at least 2 feet between each one.
Review your work on paper. Then take the extra step of transferring your spacing plan to the ceiling by placing a piece of painter's tape in the position of each light. Walk around the room and make any revisions, thereby coming full circle – literally – with your four-part planning process.