Guides · updated October 22, 2026

M4A to MP3 quality

Does converting M4A to MP3 lose quality? Yes. Here is how much, why the MP3 can be larger, and how to choose a bitrate without stacking unnecessary loss.

Tested: 22 October 2026 · 5 s AAC fixtures at 96, 128 and 256 kbps · Chrome 156, Firefox 157, WebKit 27.2

Short answer

Yes, converting M4A to MP3 loses a little quality. M4A usually holds AAC, which is already lossy; MP3 is a different lossy codec, so the audio is decoded and encoded again. At 192–320 kbps the second generation is small, but it cannot be undone. Keep the M4A as the master.

Two lossy codecs in a row

M4A is a container. Inside it, the audio is usually AAC (Advanced Audio Coding), the codec Apple uses for iTunes, Voice Memos and Apple Music downloads. AAC is lossy: it discards detail the ear is unlikely to notice, in exchange for a smaller file.

MP3 is also lossy, but it uses a different psychoacoustic model and a different frame structure. Converting M4A to MP3 is therefore not a repackaging job. It is:

Decode AAC to PCM samples.
Encode those samples with LAME at the chosen bitrate.

The second encoder starts from the already-reduced AAC signal. It cannot recover what AAC removed. That is the “second generation” problem.

How big is the loss?

It depends on the bitrate and the material.

Source	MP3 target	What to expect
256 kbps AAC music	320 kbps MP3	Usually hard to distinguish in casual listening
128 kbps AAC music	192–320 kbps MP3	A small difference on cymbals and dense mixes
64–96 kbps voice memo	128 kbps MP3	The source is the limit; the MP3 is fine for speech
128 kbps AAC → 128 kbps MP3	128 kbps MP3	The most avoidable loss; go higher

The numbers are not a guarantee. They are a guide to avoiding the obvious mistake: encoding at a lower bitrate than the source.

Why the MP3 is often larger

MP3 at 192 kbps is about:

192,000 bits/s × 60 ÷ 8 = 1,440,000 bytes ≈ 1.44 MB per minute

At 320 kbps it is about 2.4 MB per minute. A 112 kbps M4A is about 0.84 MB per minute. The MP3 is larger because MP3 is less efficient than AAC at the same quality, and because you chose a higher bitrate to avoid stacking loss.

If size is the goal, MP3 is the wrong direction. If compatibility is the goal, the size increase is the price.

The practical workflow

Keep the M4A. It is the master for anything Apple plays.
Convert once when a car stereo, older player or upload form needs MP3.
Choose a bitrate at or above the source. 192 kbps for speech, 256–320 kbps for music.
Do not convert the MP3 again. Each round trip adds another generation.

What this tool does not do

It does not decode ALAC. An M4A with Apple Lossless is refused, because the browser cannot decode it.
It does not remove DRM. A .m4p FairPlay file is refused.
It does not normalize loudness or “enhance” the audio. It changes the container and the codec, nothing else.
It does not claim lossless output. MP3 is lossy at every bitrate.

FAQ

Does converting M4A to MP3 lose quality?

Yes. Both are lossy formats. The AAC audio is decoded to PCM and encoded as MP3, which adds a second generation of lossy compression. The loss is usually small at 192–320 kbps, but it is real and irreversible.

Is M4A higher quality than MP3?

At the same bitrate, AAC usually sounds better, which is why Apple uses it. That does not mean every M4A is high quality: a 64 kbps voice memo is still a 64 kbps voice memo. Convert for compatibility, not for an upgrade.

Why is the MP3 bigger than the M4A?

MP3 at 192 kbps is about 1.44 MB per minute, fixed by the bitrate. A 112 kbps M4A is about 0.84 MB per minute. The MP3 can be roughly 1.7 times larger. You are converting for compatibility, not to save space.

Can I convert without losing quality?

No. There is no lossless M4A-to-MP3 path. You can keep the M4A and convert only when a device needs MP3, or export a WAV from the original if you have a lossless master.

What bitrate should I choose?

Match or exceed the source. A 256 kbps iTunes AAC deserves 320 kbps MP3; a 64–128 kbps voice memo is fine at 128 kbps. Converting a 96 kbps source to 320 kbps does not add detail.