There are many ways to do a factory reset on an Android phone. But before that, it’s always wise to make a backup – especially of contacts, photos and messages.
I’ll list them out as simple as possible.
If the phone is turned on and accessible
- Go to Settings > (Personal) Backup & Reset > Factory Data reset > Reset phone
- Some phones allow you to leave the phone memory photos and files as it is at this point.
If the phone is turned off and/or locked
- Power off the phone
- Keep the volume up button pressed, and simultaneously press the power up button for a few seconds till it turns on
- Phone should load into boot screen
- Use volume up and down to highlight Factory reset and power button to select the option
If your phone is stolen and you want your data erased
- Open Android Device Manager (https://www.google.com/android/devicemanager) in a computer
- Login with the Google account used on your phone/tablet of interest
- You can make it ring, lock it or Erase
- Click Erase and continue