With an “average” cell phone size of ~3700 mAh a full Slim charge will support roughly 45% increased use time. If YOUR typical phone discharge is 9 hours of use the Slim will provide (.45 x 9)  4 Hrs. of your additional full function with calls, streaming, email etc. If a full charge lasts you 12 Hrs. based on your use patterns Slim will provide 5.4 Hrs. of additional use. (See reference table for range of phone cell sizes and use rates)