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.
Don’t despair! Measuring and labelling light output instead of energy use actually makes it easier for you to find the right energy efficient bulb for your space. Use this chart to determine how many lumens you’ll need from your next light bulb. For example, if you typically purchase 60W incandescent bulbs, which produce about 700-800 lumens, consider purchasing a lower energy alternative like a 42W halogen bulb, 12W CFL, or even a 10W LED bulb to achieve the same brightness.
source https://www.thelightbulb.co.uk/resources/lumens_watts/