This is a reference page. If you just want step-by-step instructions, read how to make a custom iPhone ringtone. If you want to know why a file is accepted or rejected — and how to check one before you sync it — read on.
The specification at a glance
| Property | What the iPhone expects | Notes |
|---|---|---|
| Container | MPEG-4 audio (the same container as .m4a) | Boxes such as ftyp, moov and mdat |
| Extension | .m4r for computer sync | The Files app method also accepts .m4a and .mp3 |
| Codec | AAC-LC | Use AAC; MP3 audio renamed to .m4r is rejected |
| Sample rate | 44.1 kHz or 48 kHz | 44.1 kHz is the usual choice |
| Channels | Stereo or mono | The phone speaker is effectively mono; stereo costs nothing at ringtone sizes |
| Bitrate | 128–256 kbps | 192 kbps is a sensible default |
| Maximum length | 40 s (M4R sync) / under 30 s (Files app, GarageBand) | See the table below |
| Copy protection | None allowed | Apple Music and other streamed tracks can’t be used |
M4R is just M4A with a different name
An .m4r file is byte-for-byte the same kind of file as an .m4a: AAC audio packed into an MPEG-4 container. The only difference is the extension, which tells Finder and iTunes to file it under Tones instead of the music library. That has two practical consequences:
- Renaming M4A to M4R works — as long as the M4A holds AAC audio and is short enough. Some M4A files contain Apple Lossless instead of AAC; convert those to AAC first.
- Renaming MP3 to M4R does not work. An MP3 is a stream of MPEG audio frames with no MPEG-4 container at all, so the iPhone can’t read it as a tone, whatever it is called. It has to be re-encoded to AAC, which is what the M4R option in the MP3 to M4R converter does.
Length limits by method
There isn’t one length limit — there are three, and each installation route enforces its own.
| Method | Accepted files | Length limit | What happens if it’s too long |
|---|---|---|---|
| Files app → Share → Use as Ringtone (iOS 26+) | M4A, MP3 | Under 30 s | The option is missing or iOS says the file is too long |
| GarageBand on iPhone → Share → Ringtone | Any audio GarageBand imports | Up to 30 s | GarageBand offers to shorten it automatically — from the start |
| Finder (Mac) or iTunes (Windows) sync | M4R | 40 s | The file is silently ignored; no error is shown |
Two details catch people out. First, “under 30 seconds” really means under: a clip of exactly 30.00 s can be refused, and AAC encoders add a few milliseconds of priming and padding, so aim for 29 seconds. Second, the 40-second sync limit is silent — Finder appears to copy the file and nothing arrives. If a synced tone is missing, check its length before anything else. The ringtone maker here warns you as soon as a selection crosses either limit and offers a one-click “Cut to” fix.
How long should a ringtone actually be?
The limit is not the target. An iPhone loops the ringtone for as long as the phone rings, and most calls ring for something like 20–30 seconds before going to voicemail (your carrier sets this). A 15–25 second excerpt that loops cleanly is often better than a full 40 seconds that gets cut off mid-phrase. Choose the excerpt so it starts on the hook and ends with a 1–2 second fade, so the loop point is smooth.
Text tones and other alerts are different: they play once, not in a loop. Apple doesn’t publish a separate limit for them, but anything longer than a few seconds is annoying in practice. Keep alert tones to 1–5 seconds — the notification sound maker starts at 4 seconds with fast fades.
File size
Ringtones are tiny. Because AAC is a constant-bitrate format here, the size is just bitrate × duration ÷ 8:
| Length | 128 kbps | 192 kbps | 256 kbps |
|---|---|---|---|
| 5 s (alert) | 80 KB | 120 KB | 160 KB |
| 29 s (Files app) | 464 KB | 696 KB | 928 KB |
| 40 s (M4R sync) | 640 KB | 960 KB | 1.28 MB |
(Kilobytes here are 1,000 bytes; the container adds a few kilobytes.) Size never limits a ringtone, so there is no reason to go below 128 kbps. Above 256 kbps nothing is gained through a phone speaker. Use the audio file size calculator for other combinations.
Loudness
There is no volume requirement, but Apple’s built-in tones are mastered loud. A song excerpt from a quiet verse can be hard to hear next to them. Normalizing the clip so its peak sits at −1 dBFS brings it up as far as possible without distortion; see peak vs loudness normalization for when that isn’t enough.
How to check a file before you sync it
- Mac: select the file in Finder and press ⌘I. Kind should say MPEG-4 audio (or Ringtone), and Duration should be 40 seconds or less. In Terminal,
afinfo ringtone.m4rprints the data format — look foraac— and the exact duration in seconds. - Windows: right-click the file → Properties → Details shows Length and Bit rate. If Length is missing, Windows couldn’t read the file as MPEG-4, which usually means a renamed MP3.
- iPhone: long-press the file in Files and choose Get Info to see its size and kind.
Troubleshooting by symptom
| Symptom | Likely cause | Fix |
|---|---|---|
| Synced tone never appears | Longer than 40 s, or an MP3 renamed to .m4r | Export a real M4R of 40 s or less |
| No “Use as Ringtone” in Files | 30 s or longer, iOS older than 26, or an unsupported format | Export an M4A or MP3 of about 29 s |
| GarageBand cuts the wrong part | Clip over 30 s, auto-shortened from the start | Trim to the part you want before importing |
| Can’t open the song at all | DRM-protected streaming download | Use a file you own, such as a purchased MP3 |
| Ringtone is much quieter than others | Quiet source passage | Normalize to −1 dBFS before exporting |
Once a custom tone is installed it appears at the top of Settings → Sounds & Haptics → Ringtone, above Apple’s tones, and can be assigned to individual contacts from the Contacts app. Building the file on a computer? The Mac and Windows pages cover the sync step for each system, and the iPhone page covers doing it all on the phone.