WAV is what recorders, audio interfaces and editing software produce by default: raw PCM samples, no compression. That is ideal while you edit and a nuisance when you want to send, upload or carry the result. A three-minute song in CD quality is over 30 MB as WAV, too big for many e-mail attachments and slow on a mobile connection. As MP3 it is around 4 MB and plays everywhere, from a phone to a car stereo from 2005.
File size: the arithmetic
Uncompressed audio size is simple to calculate: sample rate × bit depth × channels. CD audio is 44,100 × 16 × 2 = 1,411,200 bits per second, i.e. 1411 kbps or about 10.6 MB per minute. Studio recordings at 24 bit are bigger still.
| Source | Bitrate | Per minute | Fits into 100 MB |
|---|---|---|---|
| WAV 16 bit / 44.1 kHz stereo (CD) | 1411 kbps | 10.6 MB | about 9.5 minutes |
| WAV 24 bit / 48 kHz stereo | 2304 kbps | 17.3 MB | about 5.5 minutes |
| WAV 24 bit / 96 kHz stereo | 4608 kbps | 34.6 MB | under 3 minutes |
| MP3 VBR (our output, average) | ~190 kbps | ~1.4 MB | over an hour |
| MP3 128 kbps CBR | 128 kbps | 0.96 MB | |
| MP3 320 kbps CBR | 320 kbps | 2.4 MB |
The free limit is 100 MB per uploaded file, so the left side of the table matters. A whole album as one WAV will not fit, individual tracks will. You can upload up to 10 files at once and download all MP3s as a ZIP.
How our converter encodes the MP3
We encode MP3 with a variable bitrate (VBR). The bitrate adapts to the music: dense passages get up to 320 kbps, silence and simple sounds much less. The average for music is around 190 kbps, usually between 170 and 210 kbps. In listening tests this quality is generally considered transparent, meaning most people cannot reliably tell it from the WAV.
- Bit depth does not matter. MP3 has no fixed bit depth, 16-bit and 24-bit WAV both work.
- Sample rate: 44.1 and 48 kHz are kept. MP3 supports at most 48 kHz, so 88.2 or 96 kHz recordings are resampled to a supported rate.
- Channels: mono stays mono (and the file is smaller), stereo stays stereo, multichannel WAV is mixed down to stereo.
- Tags: title, artist and other fields from the WAV's INFO chunk are copied into the ID3 tag.
- No processing: no normalisation, no trimming, no fade.
The bitrate cannot be changed. If a radio station or a distributor asks for exactly 320 kbps CBR, export the file locally, for example in Audacity with a constant bitrate of 320 kbps.
Which bitrate do you actually need?
- Speech, dictation, voice notes: 64 to 96 kbps in mono is plenty. Our VBR output is more than enough and still small for mono files.
- Music for listening: VBR around 190 kbps (our setting), or 256–320 kbps if you want extra headroom. 128 kbps CBR can produce audible artefacts on cymbals and applause.
- Delivery to a third party: follow their specification. Often they want WAV or FLAC anyway, never send an MP3 to a mastering engineer.
Common problems
The MP3 crackles in loud passages
Masters that peak right at 0 dBFS can clip slightly after MP3 decoding, because the encoded waveform overshoots the original. Leave about 1 dB of headroom when exporting the WAV and the problem disappears.
Converting the MP3 back to WAV does not restore quality
MP3 is lossy. What was discarded during encoding is gone. Keep the original WAV as your archive copy and treat the MP3 as a distribution copy. If you need a smaller file without any loss, FLAC typically cuts the size to roughly half.
The WAV will not upload or will not open
Classic WAV stores its length in a 32-bit field, so it cannot exceed 4 GB; larger recordings use RF64 or W64. That is far above our 100 MB limit anyway. Files from some dictaphones contain compressed audio (ADPCM, GSM) inside a WAV wrapper. Our converter reads most of them, so try the upload before converting elsewhere.
Alternatives without an online converter
- Audacity (free, all systems) exports MP3 directly and lets you set the bitrate, normalise and trim.
- Music app on macOS: in Settings → Files → Import Settings choose MP3 Encoder, then File → Convert → Create MP3 Version.
Online conversion is practical on a phone, on a computer where you cannot install software, or when you just need a handful of files done. If you have video rather than WAV, see MP4 to MP3.
A bit of history
WAV (Waveform Audio File Format) was introduced by Microsoft and IBM in 1991 as part of the RIFF container for Windows 3.1, see the Library of Congress description. MP3, formally MPEG-1 Audio Layer III (ISO/IEC 11172-3, 1993), was developed largely at Fraunhofer IIS in Erlangen. For years encoders had to be licensed. The licensing programme ended on 23 April 2017 and the patents have expired (Fraunhofer IIS), so MP3 can now be encoded freely in any software.