How to Calculate Lumens Per Watt
- 1). Lumens are the amount of light produced by a bulb. Find the number for lumen output on the light bulb's box.
- 2). Wattage is the amount of electricity needed to light the bulb. The higher the wattage is, the brighter the light will be. You can find the bulb's wattage written both on the box and on the bulb itself.
- 3). Divide the light bulb's lumen output by the number of watts the bulb needs. For example, a 100-watt light bulb usually has 1800 lumens, so the LPW is 18.