How Audio File Size is Calculated
The size of an audio file depends on whether it uses uncompressed or compressed encoding.
Uncompressed audio (PCM, WAV, AIFF): Every sample is stored at full precision. The formula is:
File size (bytes) = Sample rate (Hz) x Bit depth (bits) x Channels x Duration (seconds) / 8
The division by 8 converts bits to bytes. For CD-quality stereo audio (44,100 Hz, 16-bit, 2 channels), 1 second of audio occupies 44,100 x 16 x 2 / 8 = 176,400 bytes. A 3-minute track is 176,400 x 180 = 31,752,000 bytes (approximately 30.3 MB). WAV and AIFF files add a small header (typically 44 bytes for WAV), so the actual file is fractionally larger than the raw PCM data.
Compressed audio (MP3, AAC, OGG Vorbis, Opus): The encoder discards audio information that is less perceptible to human hearing (a technique called perceptual coding). The output bitrate determines file size regardless of original sample rate or bit depth:
File size (bytes) = Bitrate (bits/second) x Duration (seconds) / 8
A 3-minute MP3 at 128 kbps is 128,000 x 180 / 8 = 2,880,000 bytes (approximately 2.75 MB), roughly 11 times smaller than the equivalent WAV file.
Worked Example
A 3-minute stereo recording at CD quality (44,100 Hz, 16-bit, 2 channels) with the default settings produces:
| Value | Calculation | Result |
|---|
| Raw bytes | 44,100 x 16 x 2 x 180 / 8 | 31,752,000 bytes |
| Kilobytes | 31,752,000 / 1,024 | 31,007.81 KB |
| Megabytes | 31,752,000 / 1,048,576 | 30.28 MB |
| Gigabytes | 31,752,000 / 1,073,741,824 | 0.030 GB |
This matches the calculator's default output above.
Common Format Reference
| Format | Type | Typical size per minute (stereo) | Use case |
|---|
| WAV / AIFF (16-bit, 44.1 kHz) | Uncompressed | 10.1 MB/min | CD audio, final masters |
| WAV / AIFF (24-bit, 48 kHz) | Uncompressed | 16.5 MB/min | Video production audio |
| WAV / AIFF (24-bit, 96 kHz) | Uncompressed | 33.0 MB/min | Studio recording |
| FLAC (lossless compressed) | Lossless | ~5 MB/min | Archival, audiophile playback |
| MP3 (128 kbps) | Lossy | 0.94 MB/min | General music streaming |
| MP3 (320 kbps) | Lossy | 2.34 MB/min | High-quality streaming |
| AAC (128 kbps) | Lossy | 0.94 MB/min | iTunes, Apple Music |
| OGG Vorbis (128 kbps) | Lossy | 0.94 MB/min | Open-source applications |
| Opus (96 kbps) | Lossy | 0.70 MB/min | VoIP, podcast streaming |
Lossless vs Lossy Compression
Lossless compression (FLAC, ALAC, Apple Lossless) reduces file size without discarding any audio data. When you decompress a FLAC file, you get the exact original PCM waveform back. Typical compression ratios are 40 to 60 percent, so a 30 MB WAV becomes roughly 12 to 18 MB as FLAC. This calculator does not simulate FLAC because the compression ratio varies by audio content; quiet recordings compress more than dense mixes.
Lossy compression (MP3, AAC, OGG, Opus) permanently removes audio information using psychoacoustic models that identify sounds unlikely to be perceived clearly. At high bitrates (256 kbps or above), most listeners cannot distinguish a well-encoded MP3 from the original WAV. At low bitrates (below 64 kbps), artefacts such as ringing around transients and loss of stereo depth become audible.
Storage Planning for Recording Projects
Knowing your expected file sizes helps you plan storage for recording sessions. A useful rule of thumb for 24-bit, 48 kHz stereo recording (common in video and podcast production) is approximately 17 MB per minute. A 2-hour interview session produces around 2 GB of raw audio. If you are recording multiple microphone tracks simultaneously, multiply by the number of tracks.
For podcast distribution, MP3 at 128 kbps is the industry standard. A 60-minute podcast episode is approximately 57 MB. Hosting services typically allow 500 MB to 5 GB per month on free or entry-level plans, so a weekly 60-minute podcast uses around 228 MB per month.
Related Calculators
Sources and method: Uncompressed audio size uses standard linear PCM arithmetic as stored in the WAV (RIFF) and AIFF container formats. Compressed bitrate arithmetic per ISO/IEC 11172-3 (MPEG-1 Audio, MP3) and ISO/IEC 13818-7 (MPEG-2 AAC). Binary unit definitions (1 KB = 1,024 bytes) per IEC 80000-13.
This calculator gives estimates for raw audio data. Actual file sizes include container headers (typically 44 bytes for WAV, variable for MP3 ID3 tags) and may differ slightly. FLAC and other lossless compressed formats are not modelled because their compression ratio depends on audio content.
