## LUMENS ARE THE NEW UNIT OF MEASUREMENT FOR LIGHT BULBS

For decades, we’ve been buying light bulbs according to wattage. But as energy efficient, low-watt light bulbs like CFLs and LEDs have become readily available, watts have become an unreliable metric for selecting bulbs.

Instead of focusing on wattage, which measures power or energy use, manufacturers are indicating the brightness of their energy efficient bulbs according to lumens, which measure light output. So while we may be accustomed to shopping for bulbs according to wattage, lumens are actually a more accurate measurement of how bright your light will be.

### CONVERTING LUMENS TO WATTS

How many lumens are in a watt? Because lumens measure brightness and watts measure energy output, there is no simple method for converting wattage to lumens. With energy efficient lighting like LEDs and CFLs, how many lumens are in a 60W bulb or 100W bulb depends on the lumen output of the bulb, not its energy use.

### Lumens to watts calculation formula

Energy saving lamps have high luminous efficacy (more lumens per watt).

The power P in watts (W) is equal to the luminous flux ΦV in lumens (lm), divided by the luminous efficacy η in lumens per watt (lm/W):

P(W) = ΦV(lm) / η(lm/W)

### Lumens to watts table

LumensIncandescent
light bulb
(watts)
Fluorescent
/ LED
(watts)
375 lm25 W6.23 W
600 lm40 W10 W
900 lm60 W15 W
1125 lm75 W18.75 W
1500 lm100 W25 W
2250 lm150 W37.5 W
3000 lm200 W50 W