Lumen is the SI derived unit measuring how much light you are getting from a bulb.
While watt is a unit of power measuring the amount of energy an item needs to function.
Formula to convert W to lm.
Converting these units is like measuring how well a light source converts energy into light.
For a 100 W incandescent bulb produces about 1,600 lumens, for an efficiency of 1,600/100 = 16 lumens per watt.
A halogen bulb consumes only 72 watts for the same amount of brightness, making its efficiency to be 22 lumens per watt.
A CFL bulb consumes 26 W making its efficiency to be 61 lumens per watt.
LED bulbs, which are the most efficient, consume only 22 watts for an efficiency of 73 lumens per watt.
Example:
Convert 75 watts incandescent bulb if its efficiency is 15 watts per lumen and you asked to convert the energy to lumens per watt.
= 75 x 15
=1125 Lumens.
= 800 lumens.
