How to find a lost phone

This works if someone is holding the phone and can answer. If nobody can, start with the phone's own account, below.

A number alone cannot locate it. The account already on the phone can. Four things, in order.

01Android: Find Hub

Where
android.com/find, any browser, the phone's Google account
You can
Ring it, lock it with a message, erase it
Limits
The phone must be on and online. Some models report a last position after going offline.

02iPhone: Find My

Where
icloud.com/find or the Find My app on another Apple device
You can
Mark as Lost: lock it and show a number on the screen
Limits
Find My had to be on before it was lost. Recent iPhones can be found while off.

03Samsung: SmartThings Find

Where
smartthingsfind.samsung.com, the Samsung account
You can
Same as Find Hub, plus offline finding through nearby Galaxy devices

04Carrier, then police

Carrier
Suspend the SIM so verification codes stop arriving on it
Police
Give them the IMEI from the box or your carrier account. Insurance usually wants the report.
Then
Change banking and email passwords from another device

05FAQ

Can I find my lost phone with just the number?

No. A number identifies a line, not a place. The phone's own account, Find Hub or Find My, is what locates it.

Can I locate a lost phone for free?

Yes. Find Hub, Find My and SmartThings Find are free and already on the phone.

Can a lost phone be tracked when it is off?

Recent iPhones and some Android models report a position for a while after switching off. Older phones show their last known position only.

Can the police track my phone?

They can ask the carrier, with a warrant, in serious cases. For an ordinary loss they take the IMEI and the report.

Someone is holding it