For this let your battery drain completely and let it turn it off on it's own. Turn on the phone and turn it off. Plug in the charger without turning on the phone and let the onscreen indicator shows 100%. When it is 100% unplug the charger and switch on your phone. Plug in the charger and let the onscreen display shows 100%. Unplug the charger and let the battery discharge to 0% and turn off the phone on it's own. Fully charge the battery without any interruption. In this way you have recalibrated your phone battery
