How long can iPhone ringtones be?

The longest time for iphon to customize ringtones is 40 seconds.

Ringtone setting operation is:

Step 1: Log in to Apple official website, download itunes software, install it and open it.

Step 2: Connect the iPhone6 to the computer with a data cable.

Step 3: Click the "More" icon in the itunes interface and select the "Ringtone" option.

Step 4: Click "File" and select "Add File to Database"; Add ringtone files to itunes. (Note: The ringtone is in m4r format, and the time is less than 40s. )

Step 5: Click the iPhone device icon to open the "ringtone" option; Click Sync Ringtones, select the ringtone file, and then click Sync under itunes to import ringtones.

For reference, I hope I can help you.