How audio file size is calculated
Audio size depends only on the bitrate and the duration:
Size (bytes) = bitrate (bits per second) × duration (seconds) ÷ 8
For uncompressed audio (WAV, AIFF), the bitrate comes from the recording format:
Bitrate = sample rate × bit depth × channels
CD audio, at 44.1 kHz, 16 bits and 2 channels, runs at 1,411.2 kbps.
Reference sizes
| Format | Bitrate | Per minute | Per hour |
|---|---|---|---|
| Podcast MP3 (mono) | 64 kbps | 0.48 MB | 28.8 MB |
| MP3 / AAC standard | 128 kbps | 0.96 MB | 57.6 MB |
| MP3 high quality | 320 kbps | 2.4 MB | 144 MB |
| FLAC (CD source) | ~900 kbps | ~6.8 MB | ~405 MB |
| WAV 44.1 kHz / 16-bit | 1,411 kbps | 10.6 MB | 635 MB |
| WAV 48 kHz / 24-bit | 2,304 kbps | 17.3 MB | 1.04 GB |
| WAV 96 kHz / 24-bit | 4,608 kbps | 34.6 MB | 2.07 GB |
The calculator uses decimal units: 1 MB = 1,000,000 bytes. Operating systems often show sizes in binary units (MiB), which look about 5% smaller for the same file.
Compressed formats
- MP3, AAC and Opus are lossy: they discard sounds the ear is unlikely to notice. At 256 to 320 kbps, most listeners cannot tell them from the CD.
- FLAC and ALAC are lossless: they shrink files to roughly 50 to 70% of WAV with no loss, but the bitrate varies with the music.
- Variable bitrate (VBR) files have an average bitrate; use that value.
Example
One hour at 320 kbps is 320,000 × 3,600 ÷ 8 = 144 MB. A gigabyte holds about 6.9 hours at that rate, or about 17 hours at 128 kbps.
Planning recordings
For multitrack recording, multiply by the number of tracks. A 2-hour session of 16 mono tracks at 48 kHz and 24 bits uses 16 × 1,152 kbps × 7,200 s ÷ 8 ≈ 16.6 GB. Record in 24-bit for headroom, then export compressed copies for sharing.