For years, we’ve measured light bulbs by watts, which indicate how much energy a bulb uses. But bulb brightness is measured in lumens. Many of the new light bulbs’ boxes list lumens and include helpful notes about how the bulb compares with the wattage you are looking to replace. An incandescent 40-watt bulb gets replaced with a 450-lumen bulb; a 60-watt bulb with a 800-lumen bulb; a 75-watt bulb by a 1,100 lumen; and a 100 watt by a 1,600 lumen.
More light bulbs are now packaged with a “Lighting Facts” label. Besides lumens, this may include factors like lumens per watt (bulb efficiency); watts (energy used to make the light); correlated color temperature, which indicates cool or warm color (about 2700 Kelvin replicates what we’re familiar with in a traditional incandescent); and a color-rendering index (the measurement of a light’s appearance on objects).