Station Audio

Audio file size and bitrate calculator

How large a recording will be, how long you can record in a given amount of space, and how formats compare. Uncompressed and constant-bitrate sizes are exact.

Format
1 mono, 2 stereo, 6 for 5.1
h:mm:ss or mm:ss

File size

42.3 MB

40.4 MiB as Windows reports it (42,336,044 bytes including a 44-byte WAV header). Bitrate 1411.2 kbps, 10.6 MB per minute. 64 GB holds 100:46:52 (h:mm:ss). A single WAV file reaches the 4 GiB limit after 6:45:48.

Common formats for 4:00

FormatBitrateSizePer hourNotes
MP3 128 kbps 128 kbps 3.84 MB 57.6 MB CBR, lossy
MP3 320 kbps 320 kbps 9.60 MB 144 MB CBR, lossy; the MP3 maximum
AAC 256 kbps 256 kbps 7.68 MB 115 MB lossy
CD audio, 44.1 kHz / 16-bit stereo 1411.2 kbps 42.3 MB 635 MB uncompressed PCM
48 kHz / 24-bit stereo 2304 kbps 69.1 MB 1.04 GB uncompressed PCM
96 kHz / 24-bit stereo 4608 kbps 138 MB 2.07 GB uncompressed PCM
48 kHz / 24-bit mono 1152 kbps 34.6 MB 518 MB one track of a multitrack session
48 kHz / 32-bit float mono 1536 kbps 46.1 MB 691 MB one float track

How to use it

Pick uncompressed or compressed. For WAV, AIFF, BWF or raw PCM, set the sample rate, bit depth and number of channels; for a multitrack session enter the total number of tracks as channels, since a 24-track session at 48 kHz / 24-bit is simply 24 mono files. For MP3, AAC, Opus or any other constant-bitrate format, enter the bitrate in kilobits per second. Then give a duration and, optionally, how much storage you have. The table shows the same duration in common formats for comparison.

The formulas

The WAV header is taken as the canonical 44 bytes. Real files often carry more: broadcast WAV adds a bext chunk with timestamps, and many recorders add metadata or padding. That is usually a few kilobytes, which is irrelevant for anything but very short files. AIFF has a similar header of a different size. Audio data sizes are exact.

Worked example. An hour of 48 kHz / 24-bit stereo: 48,000 × 24 × 2 = 2,304,000 bits per second, which is 288,000 bytes per second. Multiply by 3,600 and you get 1,036,800,000 bytes: 1.04 GB, or 989 MiB. A 64 GB card holds just over 61 hours of it, and a single WAV file hits the 4 GiB ceiling after 4 hours 8 minutes. The same hour as a 320 kbps MP3 is 144 MB.

Kilobits, kilobytes and the two kinds of megabyte

Bitrates are quoted in kilobits per second, with kilo meaning 1,000: 320 kbps is 320,000 bits, 40,000 bytes, every second. File sizes are in bytes, eight bits each. Storage adds one more trap: a "64 GB" card holds 64 × 109 bytes, but Windows will describe it as about 59.6 GB because it counts in powers of 1,024. The calculator shows both where it matters.

Where it stops being reliable

Variable-bitrate (VBR) MP3 and AAC, and all lossless compression, depend on the audio itself. A VBR file set to "about 190 kbps" may come out anywhere around that figure, and a FLAC of a quiet acoustic recording will be proportionally much smaller than a FLAC of a loud, dense master. Use the bitrate the encoder reports as an average if you have one, or treat the uncompressed size as the upper bound.

Storage figures are for audio only. File systems reserve some space, recorders often keep a margin free, and video with sound is a different calculation altogether. Where precise timing matters, compare the tempo and duration with the delay time calculator or the metronome.

Common questions

5 answers
How big is a minute of CD-quality audio?

44,100 samples a second × 16 bits × 2 channels is 1,411,200 bits per second, or 176,400 bytes per second. A minute is 10,584,000 bytes: 10.6 MB in decimal units, or 10.1 MiB as Windows reports it. An MP3 at 320 kbps is 2.4 MB a minute, about 23% of that.

Why does Windows show a smaller number than this calculator?

Windows divides by 1,024 × 1,024 and still calls the result MB; drive makers, macOS and this calculator’s first figure divide by 1,000,000. The binary figure, labelled MiB here, is what Windows Explorer shows. Neither is wrong; they are different units with confusingly similar names.

How much space does a FLAC file take?

It depends on the music, so no calculator can tell you from the settings alone. FLAC and ALAC are lossless: they store exactly the same samples as a WAV file, but compress the redundancy. Quiet, sparse or mono-like material compresses well; dense, noisy, heavily limited masters compress poorly. Use the uncompressed size here as the upper bound.

Is 32-bit float bigger than 24-bit?

Yes, by a third: 32 bits per sample against 24. Its advantage is that a 32-bit float file cannot clip internally, which is why many DAWs use it for bounces and some field recorders offer it. For final delivery, 24-bit or 16-bit fixed point is usual.

What happens when a WAV file goes over 4 GB?

The classic WAV (RIFF) format stores its size in a 32-bit field, so a file cannot exceed 4 GiB. Recorders and DAWs deal with this by splitting long recordings into several files, or by writing RF64 or BW64, extensions that use 64-bit sizes. Some older software cannot open those.

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