The short answer
Bitrate is how many kilobits of data each second of audio uses. It decides the file size almost exactly, and within one format it sets how much detail the encoder can keep. For MP3 the useful range is 64 to 320 kbps; 320 is the highest the format allows.
The converter on this page is set to WAV to MP3. Its Quality menu offers 96, 128, 192 and 256 kbit/s (192 is preselected), and the Mono (one channel) option halves the bitrate, with 64 kbit/s as the lowest value. The 320 kbps row in our test was made with the same encoder but is not in the menu, because the step from 256 to 320 adds 25 percent to the size for a difference very few people can hear.
- Speech, voice memos, lectures: 64 kbps mono, or 96 kbps if the recording has music beds
- Podcasts: 64 to 96 kbps mono for a single voice, 128 kbps stereo with music
- Music for everyday listening: 192 kbps, 128 kbps if space is tight
- Music archive when you cannot keep FLAC or WAV: 256 to 320 kbps
Try it here: WAV to MP3
Open the full tool pageHow bitrate turns into file size
For constant bitrate (CBR) MP3 the size is simple arithmetic: bytes per minute = kbps x 1000 / 8 x 60. The table below is calculated with that formula, with MB meaning 1,000,000 bytes and GB meaning 1,000,000,000 bytes. Real files are a few kilobytes bigger because of headers and tags such as cover art.
Uncompressed CD quality audio (WAV, 44.1 kHz, 16 bit, stereo) runs at 1411.2 kbps, which is 10,584,000 bytes per minute: 10.6 MB per minute in decimal units, or about 10.1 MB per minute if your computer counts in 1024 byte units, as Windows does. That is why a 4 minute WAV song takes about 42 MB.
| Bitrate | MB per minute | MB per 4 minute song | Hours in 1 GB |
|---|---|---|---|
| 64 kbps | 0.48 | 1.92 | 34.7 |
| 96 kbps | 0.72 | 2.88 | 23.1 |
| 128 kbps | 0.96 | 3.84 | 17.4 |
| 160 kbps | 1.20 | 4.80 | 13.9 |
| 192 kbps | 1.44 | 5.76 | 11.6 |
| 256 kbps | 1.92 | 7.68 | 8.7 |
| 320 kbps | 2.40 | 9.60 | 6.9 |
| WAV, CD quality (1411.2 kbps) | 10.58 | 42.34 | 1.6 |
Measured: one recording in MP3, M4A, OGG and WAV
We took a 103.6 second stereo WAV (44.1 kHz, 16 bit) of spoken English, 17,844 KB, and converted it with the Anyfeat audio converter to each setting. Sizes are in KB of 1024 bytes as the browser saved them. The per minute column is calculated as KB x 60 / 103.6, and the percentage is calculated against the WAV.
The MP3 results match the formula almost perfectly: 1,619 KB over 103.6 seconds works out to 128.0 kbps (calculated). Halving the channels halves the file: 64 kbps mono came out at 810 KB, 50.0 percent of the 128 kbps stereo file (calculated).
| Format and setting | Size (KB) | KB per minute (calculated) | Smaller than WAV (calculated) | Conversion time |
|---|---|---|---|---|
| WAV (original, re-saved) | 17,844 | 10,334.4 | 0% | 165 ms |
| MP3 64 kbps mono | 810 | 469.1 | 95.5% | 762 ms |
| MP3 96 kbps | 1,215 | 703.7 | 93.2% | 796 ms |
| MP3 128 kbps | 1,619 | 937.6 | 90.9% | 770 ms |
| MP3 192 kbps | 2,429 | 1,406.8 | 86.4% | 811 ms |
| MP3 256 kbps | 3,239 | 1,875.9 | 81.8% | 784 ms |
| MP3 320 kbps (not in the menu) | 4,048 | 2,344.4 | 77.3% | 788 ms |
| M4A (AAC) 96 kbps | 1,121 | 649.2 | 93.7% | 398 ms |
| M4A (AAC) 128 kbps | 1,463 | 847.3 | 91.8% | 407 ms |
| M4A (AAC) 192 kbps | 2,147 | 1,243.4 | 88.0% | 429 ms |
| OGG (Opus) 64 kbps | 791 | 458.1 | 95.6% | 571 ms |
| OGG (Opus) 96 kbps | 1,183 | 685.1 | 93.4% | 624 ms |
| OGG (Opus) 128 kbps | 1,578 | 913.9 | 91.2% | 661 ms |
MP3 vs M4A vs OGG vs WAV: what the numbers show
At the same nominal bitrate the three compressed formats end up close in size, because the bitrate is the budget. The AAC files came out smaller than their setting: averaged over the recording they used about 88.6, 115.7 and 169.8 kbps instead of 96, 128 and 192 (calculated from the sizes). On this speech recording the browser's AAC encoder spent fewer bits than allowed, so the 192 kbps M4A was 11.6 percent smaller than the 192 kbps MP3 (calculated). Opus stayed within about 3 percent of its target.
The bigger difference is quality per bit, which our test did not measure. It is well established that AAC and Opus reach a given quality at a lower bitrate than MP3, so 128 kbps AAC or 96 kbps Opus is a reasonable alternative to 160 or 192 kbps MP3 for listening. MP3 still wins on compatibility: every car stereo, old player, smart speaker and upload form accepts it, while OGG does not play on many car radios and older devices.
WAV is in a different class. It stores every sample, so it is 4.4 to 22.6 times larger than the compressed versions in our table (calculated), but it is the right choice for editing and for hardware that only reads uncompressed audio. Speed is not a concern for any format: the slowest conversion, 192 kbps MP3, handled 103.6 seconds of audio in 0.811 seconds, about 128 times faster than real time (calculated).
Which bitrate to use for speech, podcasts, music and storage
No listening test was part of this measurement, so the guidance below is general and widely agreed rather than a verdict from our data. Trust your own ears with your own material: convert one file at two settings and compare them on the headphones or speakers you actually use.
- Speech has a narrow frequency range, so 64 kbps mono already sounds clear; stereo adds nothing to a single microphone
- 128 kbps is acceptable for casual music, but cymbals and applause can sound swirly on good headphones
- 192 kbps is where most listeners stop hearing a difference from the original
- Keep a lossless master if you can; an MP3 archive at 256 to 320 kbps is the fallback
| Use | Suggested setting | Size per minute (calculated) |
|---|---|---|
| Voice memo, lecture, interview | MP3 64 kbps mono | 0.48 MB |
| Podcast, one or two voices | MP3 64 to 96 kbps mono | 0.48 to 0.72 MB |
| Podcast with music, audiobook | MP3 96 to 128 kbps | 0.72 to 0.96 MB |
| Casual music, phone storage | MP3 128 kbps or M4A 128 kbps | 0.96 MB or less |
| Music, safe default | MP3 192 kbps | 1.44 MB |
| Music archive in MP3 | MP3 256 to 320 kbps | 1.92 to 2.40 MB |
| Editing, mastering, archive | WAV or FLAC | about 10.6 MB (WAV) |
Common mistakes
- Converting a 128 kbps MP3 to 320 kbps: the file grows 2.5 times, but detail removed at 128 kbps never comes back. Re-encoding to a higher bitrate never restores quality, and each lossy pass loses a little more.
- Converting MP3 to WAV to improve sound: WAV only stops further loss while editing; it keeps the current quality.
- Leaving speech in stereo: a mono voice recording saved as stereo doubles the size for no gain. Tick Mono.
- Judging quality by file size alone: a 192 kbps M4A can be smaller than a 192 kbps MP3 and still sound as good or better.
- Choosing OGG for a car or an old player: check that the device reads it, or stay with MP3.
How we measured
Measured on 26 October 2026 with Anyfeat's own browser tools, the same audio converter that is on this page, running in Microsoft Edge 156 on Windows. The source was a 103.6 second stereo WAV, 44.1 kHz and 16 bit, of computer generated spoken English, 17,844 KB. MP3 files were encoded at constant bitrate with the LAME encoder the tool uses; M4A (AAC) and OGG (Opus) were encoded with the browser's built in encoders. Times are the conversion time in the browser on our test computer and will differ on yours.
We measured file size and speed only. Audio quality was not measured with a metric or a listening panel, so quality statements on this page are general guidance. Results depend on the material: music with lots of high frequency detail compresses differently from speech, and the AAC and Opus sizes may land closer to their targets on music. You can repeat the test with your own file in the converter above; nothing is uploaded.