How Much Disk Space Does One Hour of Audio Take?

One hour of uncompressed stereo PCM at 44.1 kHz and 16 bits takes about 635 MB. At 48 kHz and 24 bits it takes about 1.04 GB. Those numbers come straight from arithmetic — sample rate × bit depth × channels — because uncompressed audio has a fixed, predictable size with no dependence on the material.

The formula

Bytes per hour = (sample rate × bit depth × channels ÷ 8) × 3,600.

The sampling rate is samples per second per channel, defined in the federal digitization guidelines with its Nyquist–Shannon basis (FADGI: sampling rate). The bit depth, or word length, is how many bits encode each sample and is what determines the encoded dynamic range (FADGI: bit depth). The step-by-step version of this calculation is in how to calculate audio bit rate and file size.

Worked figures for one hour

• 44.1 kHz / 16-bit / stereo — 1,411.2 kbps → about 635 MB
• 44.1 kHz / 16-bit / mono — 705.6 kbps → about 318 MB
• 48 kHz / 24-bit / stereo — 2,304 kbps → about 1.04 GB
• 96 kHz / 24-bit / stereo — 4,608 kbps → about 2.07 GB

These are decimal megabytes (1 MB = 1,000,000 bytes), the convention drive manufacturers use. A file manager reporting binary units will show roughly 605 MiB where the table says 635 MB — same file, different unit.

Note what scales with what. Doubling the sample rate doubles the size. Going from 16 to 24 bits adds half again. Dropping from stereo to mono halves it, which is why the mono case matters for spoken-word recordings.

What FLAC changes

FLAC is lossless compression: it reduces the file while decoding back to bit-identical PCM, so the stored size no longer follows the formula. The saving depends entirely on the content — dense, loud material compresses less than sparse or quiet material — and the Xiph.Org FLAC documentation describes the encoder's prediction and residual coding stages that produce it. As a planning figure, expect a meaningful fraction off the PCM size rather than a fixed ratio, and expect spoken word to compress harder than a full mix.

The practical consequence: a FLAC library's size can only be measured, not calculated. Two albums at identical resolution can differ substantially. What FLAC does and does not discard is covered in is FLAC really lossless.

Why lossy formats are quoted differently

Lossy encoders are usually specified by a target bit rate instead, so size follows from that number directly: bit rate ÷ 8 × seconds. A constant 128 kbps stream is 16 kilobytes per second, or about 57.6 MB per hour, regardless of resolution — the encoder discards data to hit the target, so the original sample rate and bit depth no longer set the size. Variable-bit-rate encoding makes even that an estimate.

Planning archive storage

For material intended to be kept, resolution choices interact with storage budgets. The Library of Congress recommended formats statement for audio works names PCM WAVE at 44.1 kHz / 16-bit or higher among preferred formats for preservation (Library of Congress — Recommended Formats Statement: Audio). Working from the table above, a 100-hour archive at that resolution is roughly 64 GB before any redundancy; the same archive at 96 kHz / 24-bit is over 200 GB.

Two details people forget when budgeting:

• Headers and metadata add a small fixed overhead per file, negligible for long files and noticeable for thousands of short ones.
• Copies count. Storage planning is about total copies held, not the size of one master.

For what the resolution numbers themselves mean before you multiply them, see what 44.1 kHz and 16-bit actually mean.