You can determine how much battery life your iPhone has by checking its battery icon, which is located in the upper right corner of your iPhone's screen. But this icon is pretty small, and it can be hard to tell exactly how much Candy Crush playing time you have left.
Luckily, there's an easy way to get a more accurate read on your phone's remaining juice: You can display the battery percentage in the upper right corner of the screen, right next to the battery icon. Here's how:
Go to the Settings app on your iPhone.
Scroll down until you see Battery. Tap Battery to open the Battery settings menu.
Next to Battery Percentage, tap the toggle to turn it on (green is on; white is off). The battery percentage will show up next to the battery icon in the upper right corner of your screen.
In the Battery settings menu, you can also see your phone's Battery Usage over the past 24 hours or past week -- this will help you determine which apps are using most of your battery life (including simply turning your phone on -- check out the percentage next to Home & Lock Screen).