There's a little button and 4 LED lights. They are located on the side of the lifebar, right next to where you plug in the USB cable. If you press the button the blue led lights will light up. It literally says 100% 75% 50% 25% on top of them. If you have 76-100% all four will light up 51-75% 3 LED's will light up 26-50% 2 lights will light up and <25% 1 will light up.