The difference between these two is not subtle and it is not really about quality. A WAV keeps every sample exactly as it was recorded. An MP3 throws most of them away and keeps a description of what your ear would have noticed. Everything else — the sizes, the compatibility, the arguments about which sounds better — follows from that one fact.
The numbers, so the rest makes sense
At ordinary CD settings a WAV runs at 1,411 kbps: about 10 MB per minute. A three-minute song is 30 MB. The same song as a 192 kbps MP3 is about 4.3 MB — roughly a seventh. An hour of WAV is around 600 MB, which is why it is the format you cannot email and MP3 is the one you can.
That seven-to-one is not compression cleverness. It is the encoder deciding which parts of the recording you would not have heard and not storing them. Do it gently and nobody notices. Do it hard and everybody does.
When WAV is the right answer
- You are still working on it. Editing, mixing, restoring, time-stretching — anything that processes the audio again. Each lossy encode works from what the last one left, so you want the stage before any of that.
- Something demands it. DAWs, samplers, DJ software and a lot of older hardware read WAV and nothing else. That is a compatibility reason, not a quality one.
- It is the master. Keep one copy of the recording with nothing discarded, and every future format can be made from it. If you only keep the MP3, everything you make later is a copy of a copy.
When MP3 is the right answer
- Someone else has to open it. MP3 plays on more things than any other audio format — car stereos, cheap players, upload forms, software written in 2004.
- It has to travel. Email, chat, a website, a phone with a full disk.
- You are going to listen to it, not work on it. At 192 kbps and above, most people stop hearing the difference on ordinary equipment.
The trap worth knowing
Converting an MP3 back to WAV does not restore anything. It decodes the file to raw samples, so it becomes large again and every editor will read it — but what the MP3 encoder discarded is gone, and no decoder can invent it. That is genuinely useful when you are about to edit, because further processing no longer stacks compression on compression. It is not an upgrade in fidelity, and any tool that says otherwise is worth being sceptical about.
The same applies in reverse: a 320 kbps MP3 made from a 128 kbps MP3 is not better than the 128, only bigger.
What to actually do
Keep the WAV if you have it, and make MP3s from it when you need to send or play something. That is the whole rule. Converting WAV to MP3 takes a few seconds and runs in this page rather than on a server, and the other direction is here for when a piece of software insists.
If the reason you are asking is disk space rather than compatibility, there is a third answer neither of these gives you: FLAC makes a WAV roughly half the size without changing a single sample. It is the only way to get smaller without giving anything up — though the file stays much larger than an MP3, and fewer things will play it.
What “CD quality” actually means
The 1,411 kbps figure comes from three numbers multiplied together: 44,100 samples a second, 16 bits per sample, two channels. Change any of them and the size changes with it. A studio WAV recorded at 24-bit and 96 kHz runs at 4,608 kbps — more than three times a CD, around 34 MB a minute — which is why session files get large so quickly.
MP3 has no equivalent dial. It tops out at 320 kbps and normally works at 44.1 or 48 kHz, so a 24-bit master and a 16-bit one produce MP3s of the same size. The extra resolution is useful while you are working and disappears the moment you encode.
Sizes you can plan around
- One minute — WAV about 10 MB, MP3 at 192 kbps about 1.4 MB
- Three minutes — WAV about 30 MB, MP3 about 4.3 MB
- One hour — WAV about 600 MB, MP3 about 86 MB
Those are the numbers that decide most arguments in practice. An hour-long interview is a 600 MB WAV that no mail server will take and an 86 MB MP3 that most will — and for speech you would drop to 128 kbps anyway and land near 58 MB.
The one thing WAV is bad at
WAV was designed to carry samples and almost nothing else. It has no real place for a title, an
artist, an album or cover art, so those fields tend to vanish when you convert into it and were
never there to begin with when you record. MP3 carries all of them in ID3 tags, which is part of
why music libraries are full of MP3s and studio folders are full of WAVs with names like
take_04_final_FINAL.wav.
Which bitrate to pick, once you have decided on MP3, is its own question.