M4A to MP3
For the car stereo, the old MP3 player, or the software that only knows one format.
Your file
Drop a file here, or click to choose
It stays on this device. Nothing is sent anywhere.
Settings
A lossy to lossy hop
M4A holds AAC, which is already lossy, so converting to MP3 means a second round of discarding. In practice one hop at 192 kbps or higher is not something you will hear. Repeated round trips between lossy formats do accumulate, so keep the M4A as your original.
Voice memos on an iPhone save as M4A, which is the most common reason people end up here.
M4A is a container, and it matters what is inside
M4A is an MPEG-4 wrapper, and it almost always holds AAC. Occasionally it holds Apple Lossless (ALAC) instead, which is a genuinely lossless codec that happens to use the same extension. If yours is ALAC, this conversion behaves like FLAC to MP3 rather than a lossy hop: there are no earlier artefacts to preserve, so a high bitrate is worth paying for. Media info reads the codec straight out of the file and settles it in a second.
Why the file is usually here at all
AAC is a better codec than MP3 by most measures, so this conversion is a downgrade in every respect except the one that matters: what will open it. MP3 is the most universally supported audio format that has ever existed, and it plays on car stereos from 2004, cheap MP3 players, gym equipment, PA systems, DJ software, church sound desks, telephone systems and a great deal of software that stopped being updated a decade ago. Those are the reasons to convert. If everything in your chain handles AAC, keep the M4A.
Bitrate, given it is a second encode
Match or slightly exceed the source. An iPhone voice memo is typically recorded low, so 128 kbps is more than enough and 96 kbps mono is fine for a single voice. Music from a purchased or streamed M4A is usually 256 kbps AAC, which wants 256 or 320 kbps MP3 to come across without the encoder having to make hard choices about material that has already been reduced once.
One hop between lossy formats is not something you will hear. It is repeated round trips that accumulate, so the practical advice is to keep the M4A as your original and treat the MP3 as a copy made for a particular device, rather than as a replacement.
Length and metadata
The MP3 comes out the same length as the input. Tags such as title, artist and album art do not reliably survive the conversion, since the two formats store them differently; if the files are going into a library where that matters, expect to retag. To cut the recording down first, trim audio works to the millisecond and can add a fade at each end.
Common questions
Is M4A better than MP3?
At the same bitrate, yes, AAC is a newer codec and holds up better, especially below 128 kbps. MP3 wins purely on compatibility.
What bitrate should I convert at?
Match or slightly exceed the source. 192 kbps is a safe default.