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How To: Determine the Amount of Lighting Needed (or Wattage) for Any Room

With so many different shapes, sizes and styles of light fixtures available, it is easy to forget that they actually serve a real purpose… Other than to look pretty, of course!

Recently, I’ve had a number of sellers reach out to ask if the light fixture, chandelier or pendant, etc. they recently purchased will be enough light (or too much light) for their space.

Well, I have a simple method to find out!

It can seem like a daunting task to figure out how much light is needed in any room, but I assure you, it is simple… All you need is basic math and the measurements of the length and width of the room in feet!

To Calculate Wattage Needed for Any Room:

It sounds like it might be complicated, but it really is just simple math!

To start, all you need to do is multiply the length of the room in feet by the width of the room in feet. This will give you the square footage.

For example, a 16 foot long by 14 foot wide room has a square footage total of 224.

Once you have the square footage of the room, you can use it to calculate how much wattage you will need to light the room.

The reason the wattage calculation is important is because most incandescent lighting fixtures have a maximum wattage listed.

For example, a 6-light chandelier that uses incandescent bulbs might have a maximum wattage of 60 watts per light, for a total of 360 watts for the fixture. How would you know if 360 watts is enough for your two-story foyer light? Or is 360 watts overkill for the intimate breakfast nook?

To calculate the total wattage needed, multiply your square footage by 1.5.

Going back to our example of the 16’ by 14’ room, which has a square footage of 224, we would multiply 224 by 1.5 and get 336 watts.

The general lighting in the room will need to reach the 336 watts mark to ensure there is plenty of overall light.

The 3 Different Sources of Light: General Lighting, Task Lighting and Accent Lighting

General Lighting

What is general lighting and why is it important? General lighting, or ambient lighting, provides a comfortable level of brightness, allowing anyone to see and walk around in the room safely.

It is also described as the indoor version of basic sunlight and is the main essential for any lighting plan.

The best fixtures that provide general lighting for a room are chandeliers, pendants, flush and semi-flush mounts and wall sconces. Using a combo of these light types will give you the best overall lighting in the room and create visual interest too.

Task Lighting

Another important type of lighting is task lighting. And yes, is it exactly what it sounds like. Task lighting is used for performing tasks which require more direct light for the specific area you are working in.

Cooking, applying make-up, doing homework, working on hobbies, playing games or reading books will require a direct source of light rather than just the general lighting provided in the room. Table and desk lamps, swing arm wall sconces, under cabinet lighting, bath vanity, kitchen island and billiard lights are all examples of task oriented light fixtures.

You can calculate how much task lighting wattage is required using the same method as earlier. Simply calculate the square footage of the surface area you need more direct lighting on, such as a desk or counter. Multiply the square footage by 2.5 to get the suggested wattage fixture for the area.

For example, if a desk table top is 3’ by 6’, the square footage is 18. Multiply 18 by 2.5 and you get 45 watts. The 45 watts of task lighting needed for our work area will not add or subtract from the suggested 336 watts for the general lighting.

Accent Lighting

The third source of lighting used in design is accent lighting.

Accent lighting is used to add visual interest to a space by creating a focal point. The focal point can be art on the walls, the walls themselves, household plants or even the items on a bookshelf.

Regardless of the focal point, in order for it to stand out among the rest of the items in the room, accent lights must be three times brighter than the general lighting required in the space. Tack lighting and picture lamps are used to achieve such drama in a room.

If used in a space correctly, these three sources of lighting - General, Task, and Accent, also referred to as layering light - are key to achieving the best lighting possible.

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