How can I make custom iPhone ringtones with iTunes?

You can make custom ringtones from files in your iTunes library without using any additional software. Follow these instructions:

These instructions were tested using iTunes 9.0.2 on Mac OS X 10.5.8 and may vary depending on the version of iTunes and operating system you are running on your computer.

1. Choose the song you'd like to use for your custom ringtone.
2. Make a note of the beginning and ending time (this can be no longer than 40 seconds).
3. Right-click on the song you want to use for your ringtone and select Get Info.
4. Click the Options tab.
5. Make sure the checkboxes for Start Time and Stop Time are selected and enter the start and end time for your ringtone.
6. Click OK.
7. Right-click on the song again and select Create AAC Version.
8. When this is finished right-click the song a third time and make a note of the file location under Get Info -> Summary.
9. Navigate to your iTunes library and open the folder where the song is located.
10. Find the song and make sure you are looking at the right version. The AAC file clip you created will end in .m4a and if you right-click the file and choose "Get Info" the Duration (in seconds) should match the length of your ringtone.
11. Rename this file by changing the suffix from .m4a to .m4r (you will have to verify this change by clicking "use .m4r").
12. Copy the ringtone file you just renamed to the Ringtones directory in your iTunes library (Music -> iTunes -> iTunes Music -> Ringtones).
13. Close iTunes.
14. Open iTunes.
15. Under LIBRARY -> Ringtones on the left menu you should see your custom ringtone.
16. Sync your iPhone and the custom ringtone will appear on the iPhone under Settings -> Sounds -> Ringtone.

This process may not work using DRM-protected files purchased from the iTunes store. To avoid this problem use music imported into iTunes from your own CDs.