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How to calculate lux levels

Updated April 12, 2019

Most people determine lighting levels in their homes informally. They install enough light fixtures to create a comfortable and attractive setting. In the workplace, figuring light levels needs to be more precise. Proper illumination promotes safety and an efficient work environment. Lighting intensity may be measured and calculated in lux, which is the metric equivalent of the English system unit of measure, the foot-candle.

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  1. Measure the workroom or other area where you want to calculate the light intensity. Since lux is a metric system, use a tape measure to find the length and width of the area in meters. Multiply the length times the width to find the area in square meters.

  2. Figure out the total light present. The light emitted by a light bulb or lamp is measured in lumens. To find the total light present, check the specifications for the lights in the room. Add up the lumen ratings of all lights to find the total light in lumens present.

  3. Divide the total lumens by the number of square meters in the room to calculate lux. For example, if there are 3,000 lumens of lighting capacity in a room with an area of 100 square meters, you have 3,000/100 = 30 lux per square meter light intensity.

  4. Convert lux to foot-candles. One lux is equal to 10.76 foot-candles. Multiply lux by 10.76 to find the number of foot-candles per square meter. For example, if the lighting intensity is equal to 30 lux, the equivalent in foot candles works out to 322.8 foot-candles per square meter.

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Things You'll Need

  • light source specifications
  • tape measure

About the Author

William Adkins

Based in Atlanta, Georgia, W D Adkins has been writing professionally since 2008. He writes about business, personal finance and careers. Adkins holds master's degrees in history and sociology from Georgia State University. He became a member of the Society of Professional Journalists in 2009.

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