How to Calculate General Lighting in Square Feet

The lighting in your room impacts not only the utility of the space, but also is a key design element. Most nondesigners do not realize how much difference good lighting can make--or how inconvenient and disruptive poor lighting can be. Before you start to think about what kinds of lighting to use--ceiling, floor lamps, table lamps--it is a good idea to find out just how much light the space will need to be properly illuminated. Performing a simple calculation can set you on your way to creating the perfect lighting scheme for your room.

Calculate General Lighting in Square Feet
  1. Find out the length of the area. If you do not have this information, use the tape measure.

  2. Find out the width of the space.

  3. Multiply length times width to calculate the square footage. For example, if your space is 10 feet by 12 feet, your room's square footage is 120.

  4. Multiply the square feet figure by 1.5. This is the standard formula to discover how much wattage your space will need. In our example, the square footage of the room is 120. Multiply 120 by 1.5 to determine that you will need 180 watts of light--whether from table lamp, desk lamp, or ceiling fixture--to light the room adequately.