Calling your missing iPhone can resolve a near-disaster if the phone turns out to be hiding nearby, but if its ringer is silenced or if you lose the phone out of your house, calling it might not do any good. Apple's Find My iPhone tools work around these problems, pinpointing your lost device and triggering an alarm remotely, even if the phone is silenced.
Set Up Find My iPhone
Activate Find My Phone before you lose the device. Even if it's too late to help this time, turn on the feature as soon as you find your phone as protection for the future. In the Settings app, open iCloud. Sign in to iCloud or create a new account, if necessary, and then tap Find My iPhone. Switch the Find My iPhone slider on. On iOS 8 and above, optionally switch on Send Last Location, a feature that sends the phone's location to the Find My iPhone system when the battery dies so you can locate it after it shuts off.
Track a Lost Phone
With Find My iPhone enabled, you can track your phone's location from the iCloud website on any computer. Log in with your Apple ID and click Find My iPhone. The map shows a dot at the last known location of each device on your account -- green dots for online devices, gray dots for last-known locations of offline devices. Click a dot to see which device it represents and how recently it was detected.
The Find My iPhone map isn't accurate enough to find your phone within your house, but it's a good starting point to figure out whether the phone is there at all.
Find, Lock or Erase a Phone
On the Find My iPhone map, click All Devices and pick your missing phone from the list to see three options: Play Sound, Lost Mode and Erase iPhone. Click Play Sound to set off a loud alarm on the phone that lasts for two minutes or until you press a button on the phone. Unlike calling the phone, the Play Sound option won't get transferred to voicemail or be muted in silent mode, making it the best way to find a lost phone in your home. Lost Mode -- on iOS 6 and above -- locks the phone; prevents it from receiving calls, messages and alerts; and disables Apple Pay until you recover the phone. Use Lost Mode when you lose your phone out of the house and can't return to claim it right away. Erase iPhone is a last resort: If you can't find your phone and think someone took it, erase it to prevent data theft.
If you don't have Find My iPhone enabled when you lose your phone, the best way to find it is to call its number from another phone. This technique won't help if you have your phone on silent, if its battery dies or if you lose it outside. If you can't find your phone at home or the places you've recently visited, Apple recommends changing your Apple ID and other passwords, and reporting the phone missing to the police and your cell carrier. Include within the report your serial number, which you can find on the iPhone's box or receipt, or on Apple's support site if you registered the phone to your Apple ID.