How to Calculate the Best Recessed Lighting Layout

If you are embarking on a recessed lighting project, it is strongly recommended that you do a lot of research regarding the spacing of your recessed lights before you begin. It’s not a difficult process, but it can be a little tricky — you might even need to dust off your calculator. However, before you reach for a measuring tape and a pencil, you’ll have to nail down a few details about your project to give you a better idea of the spacing requirements to follow.

1. Understand Your Goal

Before you do anything, you’ll have to decide what you want to accomplish with your recessed lighting. Do you want to highlight an art piece? Are you trying to bring some warm, soft light into your living space? Does your hobby or work area simply need more light without the annoyance of cluttered fixtures?

Each one of these goals calls for its own individual spacing calculations, unique lighting kits and possibly a different installation process. What you need from your lighting will dictate how you proceed, so take a minute to decide what you are really trying to accomplish.

2. Start With A Sketch

At this point, your sketch is simply a rough plan to guide you while you begin looking at various lighting kits and considering what spacing formula you’re going to use. Use graph paper for accuracy and determine an easy to follow scale (e.g. four squares equals twelve inches). Sketch the dimensions of your space and everything within it–and take your time! Accuracy is key during the planning stages.

After you have replicated your living space on a piece of graph paper, make a few of photocopies of the draft. This way you can play around with sketching multiple lighting patterns without having to remeasure your room every single time you make a mistake or come up with a new layout idea.

3. Avoid Creating Shadowy Corners

When planning the layout of your recessed lighting, take extra care to ensure that your design won’t accidentally lead to shadowy corners in your home. Poorly lit corners can make your ceiling seem lower, which detracts from the spaciousness of the area, which in turn detracts from your home’s value. Especially if your space is already small, this isn’t the effect you want to create. To avoid shadowy corners, you’ll need to make sure the lights are the appropriate distance from the wall, which is why planning out and accurately measuring is an important step in the process.

4. Determine the Best Layout Per Room

Now it is time to actually determine the best layout of your recessed lighting. There is a reliable formula you should probably follow in order to get the best results possible from the project.

The "Spacing Formula" Explained

In short, the distance between your light fixtures should be twice the distance between the wall and your first light fixture. It’s a simple formula, but there is a sound theory behind it. First, understand that recessed lights shine in a conical shape. Imagine a triangle of light beaming downward from the fixture to help you better understand and visualize this effect.

People commonly make the mistake of spacing their lights equally from the wall and each other. This causes the triangle or cone of light to overlap and leave space untouched near either wall. When the lights are placed according to a thought-out formula, they will adequately cover the full space without gaps or overlap. Essentially, this spacing formula ensures the equal and even distribution of light throughout the room.

Calculating the Layout for Your Space

Now that you know the basic theory behind the spacing formula, you’ll need to choose the formula that fits into your space. Go back and review the original goal that you want for your space. You’ll need to select a spacing formula that will help you accomplish that goal. First, it would be wise to know how many lights you need or plan on using in the desired area. Next, you’ll choose a formula to help you find the best layout.

General Living Space:

If you intend to light a general space or a large open room, the basic formula will work great for you. Here’s what you do:

1. Determine the length and width of the room.
2. Either visualize or sketch out the room divided into uniform rows and columns.
3. Determine the number of lights that will be in each row and column.
4. Divide the total length of the row by the total number of lights in the row to determine the spacing between lights.
5. Divide the spacing between the lights by 2 to determine the distance between the wall and the first light.

Highlighting a Focal Point:

If you want to accomplish a specific task such as highlighting the room’s focal point, you’ll want to use the task-based layout calculation. For the most part, it is the same as the basic formula, unless your focal point is near a wall.

If this is the case, you’ll need to employ these modifications:

1. Determine the distance between the ceiling and the focal point (counter, floor, center table, etc.).
2. Divide the above distance by 4 to determine the spacing between the first light and the wall.

Wall-Washing:

You can also use recessed lighting to wall-wash. If you want to highlight an entire wall space or a hanging piece of artwork, follow these steps:

1. Keep your fixtures between 1.5 and 3 feet away from the wall.
2. Space fixtures equidistant from each other.
3. Place adjustable trim away from the wall.
4. Place fixed trim close to the wall.

5. Space Criterion

Space criterion–also referred to as SC, S/M ratio, S/M or space to mounting height ratio–is a number that will tell you the maximum distance you should put between light fixtures. You can find a variety of information and opinions regarding SC online, ranging from various types of indoor lighting to outdoor street lighting.

While you should still observe the spacing calculations previously discussed, keep an eye on how your spacing compares to the space criterion. Putting lights too far apart can increase your chances of unwanted shadows or ineffective accents. When in doubt, ask a professional at your local hardware store.

6. Finishing Your Lighting Plan

Now that you’ve done all of your calculations, it’s time to update your original sketch. This is where it will come in handy if you’ve bothered to create multiple drafts of your room layout. Having a revised plan for your recessed lighting layout will help everything run more smoothly when it comes time to install. With your spacing set, you can make a more accurate plan, which will also help you choose the right light kit for your home.

As you update your plan, you should also check things like the usage of various house circuits and the locations of support beams, which will prepare you for the construction phase. You probably won’t be able to fit your lights into a support beam, which could potentially interrupt your spacing. Additionally, you’ll need to allocate your light power sources so you don’t overwhelm your circuits. You might be able to solve overloaded circuits with extra long wires stretching towards remote circuits, so it’ll be helpful to understand how much wiring you’ll need beforehand.

Recessed lighting involves more than a design. More than likely, you’ll have to deal with your house’s internal wiring and circuits. If you haven’t done this type of project before, consider seeking advice from a professional, including the associates at your local home improvement store.