Although there are several apps for non-rooted devices that can calibrate the battery, there are some issues with it. So the safest method is discussed here - 1. Turn on the device / charge until the battery level is full (100%) and keep it connected for the next one hour. Disconnect the device from the charger and immediately turn the power off or off. When the device is off, keep it connected for one hour. Turn the device power on or off while the charger is on and keep it connected for one hour. Disconnect the device from the charger and immediately turn the power off or off. When the device is off, keep it connected for one hour. Now disconnect the device from the charger and use it normally until the battery is completely depleted. The next time you charge, you have to wait until it is 100%. . Done! This time the operating system will get a better idea about the battery of the device , so that it will give the correct statistics in the future.