In general, it should take anywhere from 3-5 hours to fully charge your LeapReader via a USB cord connected to your computer or via the LeapFrog Adapter (wall charger - sold separately) accessory. However, if you are charging with a USB cord and your computer goes to sleep, the LeapReader will suspend charging until the computer is "awake" again. You can disable the sleep mode in your computer while charging to ensure the device continues to charge while you are away from your computer. Additionally, if your LeapReader has completely discharged (and has not been charged in several months), it may take longer for the device to fully charge (8-10 hours). You will know the device is fully charged when the battery light on the side of the LeapReader turns green (the battery light is a yellow-orange color while the device is charging).