In the example below, you can see a typical open floor plan that combines a kitchen, dining nook, and family room.
For more specialized applications, count the items or areas you want to light, and use the general rule of one inch of lighting fixture to one square foot of light. More complex formulas are available, but this basic rule simplifies the calculation process while providing excellent results for home lighting applications.
Once you know how many lights a room needs, you can use this placement calculator to create a reflected ceiling plan.
Space the lights in such a manner that they appear symmetrical; doing this may add or subtract a light or two from your estimate, but it will enhance the overall appearance of the fixtures and improve the evenness of the light distribution. Always space lights an even distance from one another when using them for whole-room applications. When lighting an artwork or tapestry, always place the light at least four inches from the wall, taking into account the size of the light and the distribution it produces.
Before you get started, you’ll need to know two things; the room’s dimensions (length, width, ceiling height) and the beam angle of the light bulbs or LEDs that you’ll be using.
You can use the calculator to the right to get an idea of how many lights a room will need.
A common misconception is that tall ceilings require more lights, but that’s not always the case. Tall ceilings allow the cones of light more distance to spread so they’ll easily provide coverage for the room.
If the lights will be installed in a ceiling taller than 16-feet, you may also want to use PAR type light bulbs. They have a tighter beam control which will get more of the light down from the ceiling to the surface plane.
Determining how many recessed lights a room needs is one of the first steps when planning the lighting for a room.
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The purpose of the lights is an important factor in determining how many fixtures are needed. Consider what you want the lights to accomplish—are they highlighting a beautiful work of art or tapestry that you want to draw attention to? Are they creating a work space or craft area where shadows will be a problem? Are you using them to light your favorite reading area, or an entire room? Knowing the purpose of the light will help you to decide how far you need it to reach, how bright you need it to be, where each light should be placed, and how many lights will make your project a success.
For general lighting purposes, you’ll want to provide 1.5 watts of lighting per square foot of space in the room. So, to get the amount of lights you’ll need in the room, first measure to get the room’s square footage. Multiply by that 1.5 to get the number of watts needed for that space. Finally, you will divide this by the number of watts your planned light fixture uses to get the number of fixtures the room will need. If your fixtures use LED lights, all you have to do is check the wattage equivalent provided on the bulbs and follow the same calculation.
Now take a look at the next example. Each area is defined for measuring and calculating the number of lights separately. The imaginary walls provide reference points to determine the size of each area and the number of lights needed.
Determine How Many Recessed Lights you Need Determine How Many Recessed Lights you Need
Once you know how many lights are needed, you can decide on a layout and calculate their placement.
Another important consideration when determining how many lights to install is the wattage of the lights and the limits of your breaker. Determine the wattage of each light and multiply it by the number of lights you’d like to install, then add this number to the current electrical load on your breaker. If this number is too high, it will be necessary to install a new circuit breaker, and possibly to upgrade the electrical service to your home, if it’s a particularly large project. Using compact fluorescent bulbs in your fixtures can significantly reduce the load on your breaker, allowing for more lights without the cost of upgrading service.
To calculate for general lighting, you’ll need to measure the length and width of the room or area. If you have a large room or an open floor plan, think of each living area within as a separate room.
Most often you’ll be better off installing brighter lights rather than more lights.
Some manufacturers do not list the beam angle on their packaging. They may just say flood or spot type. In that case you can use a default of 55-degrees for BR type flood lamps, and 45-degrees for PAR type flood lamps.
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To determine how many recessed lights are needed to light any particular area, it is essential to consider the wattage of each light, its purpose, and the available power resources. Planning out this aspect of your lighting project in advance can save many hours and dollars by ensuring that everything is done properly the first time, without the need to replicate work or materials. A little strategy and know-how goes a long way to making any recessed lighting project a breeze!