Look at the left header and pick out the bulb type you have, pull up the bulb, and you'll find the lumens your after. If you have another type of light, pull up that type in the left menu, and find your bulb and wattage. The lumens will all be there for you to see.
Take into account that initial lumens will be deceiving. Mean lumens is really what you need to go by if you want the most out of your grow.