Convert WAV to MP3 on iPhone
This is the conversion MP3 was designed for: an uncompressed lossless source, encoded once. Expect roughly a tenfold size reduction and, at a sensible bitrate, very little you can hear.
Why this one is worth doing
A WAV file is raw, uncompressed PCM — the actual sample values, written to disk with a small header on the front. Nothing has been thrown away, which is why WAVs are enormous: a stereo 44.1 kHz 16-bit WAV runs about 10 MB per minute. An hour-long interview is well over half a gigabyte.
MP3 is lossy, so encoding one does discard audio. But because your source is a lossless master, the MP3 encoder is working from the real thing rather than from someone else's leftovers. This is a first-generation encode — the best MP3 you can make from this recording. It is a completely different proposition from transcoding an M4A or another MP3, where the damage compounds.
The size arithmetic
MP3 file size depends on the bitrate you choose and the length of the audio. The source WAV's size is irrelevant to the result.
- 320 kbps — about 2.4 MB per minute. Roughly a quarter the size of the WAV, and the safest choice for music.
- 256 kbps — about 1.9 MB per minute. Convexy's default.
- 192 kbps — about 1.4 MB per minute.
- 128 kbps — about 1 MB per minute. Fine for speech, thin on music.
A 60-minute WAV at ~600 MB becomes a ~144 MB MP3 at 320 kbps, or a ~59 MB MP3 at 128 kbps. If that recording is a lecture or an interview, switch channels to Mono as well and halve it again — speech captured on one microphone is not stereo in any meaningful sense.
Worth knowing: iOS has no MP3 encoder of its own. Apple's audio frameworks will happily decode an MP3, but they will not write one — the MP3 encode format is simply absent from the system's encoder list, and always has been. Convexy carries LAME, the standard open-source MP3 encoder, and runs it on your device. That is why this works with the network off.
Keep the WAV
Once you have made the MP3, the discarded audio is gone from that file forever. If the WAV is a recording you cannot repeat — an interview, a gig, a field recording, a take — keep it. Converting the MP3 back to WAV later will not bring anything back; it will simply produce a large file containing the damaged audio.
If the WAV is only large and not precious, and you want to keep every last bit while reclaiming about half the disk space, convert it to FLAC instead. FLAC is compressed but lossless: it decodes back to the exact same samples.
Sample rate: leave it alone unless you have a reason
Convexy lets you preserve the source sample rate or force 44.1 kHz or 48 kHz. Preserve is almost always right. The two exceptions worth knowing:
- A podcast host or submission form that specifies 44.1 kHz. Set it, and do not argue.
- A 96 kHz field recording that you are publishing rather than editing — resampling to 48 kHz makes the MP3 smaller at the same bitrate quality, because the encoder is not spending bits on frequencies no one can hear.
Resampling is not free — it is a real signal-processing step — but from a lossless source, at these rates, it is not the thing that will limit your quality. The bitrate is.
How to do it
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Bring the WAV into Convexy
Tap Browse files and pick it from Files or iCloud Drive, or share it into Convexy from whichever app recorded it.
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Choose MP3
Convexy lists only the formats a WAV can actually become — MP3, M4A, AIFF, CAF and FLAC.
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Set bitrate, sample rate and channels
320 kbps for music. For speech, 128 kbps and Mono will cut the file dramatically with no meaningful loss.
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Convert
The bundled LAME encoder runs on your iPhone. A long recording takes a moment; nothing is uploaded.
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Save or share it
Rename the output if you need a specific filename, then save to Files or send it on.
Common questions
Does WAV to MP3 lose quality?
Yes — MP3 is a lossy format and permanently discards audio. But this is the least harmful way to make an MP3, because the source is lossless and the encoder only runs once. At 320 kbps, from a clean WAV, most listeners on most equipment will not reliably tell the difference. That is a far cry from converting an M4A or another MP3, where the loss stacks.
What bitrate should I use for WAV to MP3?
320 kbps for music you care about. 256 kbps is a sensible default. For speech — lectures, interviews, voice notes — 128 kbps in Mono is plenty and produces a file a tenth the size, which matters when a submission form has an upload cap.
Can I convert the MP3 back to WAV to recover the quality?
No. You will get a WAV about ten times the size of the MP3 containing exactly the same damaged audio. Decompressing a lossy file does not restore what the encoder deleted. Nothing does. Keep the original WAV if the recording matters.
Why is my huge WAV becoming a small MP3?
Because WAV stores every sample uncompressed and MP3 stores an approximation, tuned to what human hearing actually resolves. A 10:1 reduction at 320 kbps is normal and expected. The size difference is the whole point of the format.
Does Convexy need the internet to make an MP3?
No. The MP3 encoder is compiled into the app and runs on your device. Turn on Airplane Mode and convert anyway — it works, because there is no server involved at any stage.