This article explains how to recalibrate your iPhone battery using Apple's Battery Recalibration tool. It also explains the old style of battery calibration.
How to Calibrate iPhone Battery
Apple released a battery calibration tool along with iOS 14.5 that allows you to recalibrate your battery. If you don't have iOS 14.5 or later, you'll need to update your operating system before you can use this tool.
If your phone is fully updated and has the battery recalibration feature, it will run automatically and improve your battery life over time. You can check its progress at any time in the Battery Health section of your iPhone settings.
How to use the iPhone Battery Recalibration Tool:
