How Much Space Does an Hour of Audio Take?

[TO VERIFY: What is a standard quality setting and duration for two settings for a podcast, such as mono 48 kHz 24-bit for recording and mono 128 kbps AAC for published distribution?]

The raw arithmetic works like this. In bytes, an hour of audio storage is determined by the sample rate of the recording (in samples per second), the audio bit depth (usually 8, 16, or 24 bits per sample), the number of channels (mono or stereo), and the duration of the audio in seconds:

bytes = sample rate × (bit depth ÷ 8) × channels × seconds

The example is a common setting for an audio master. A 48,000 Hz / 24-bit stereo PCM master brings in 288,000 bytes every second, or 1.04 GB per hour.

The Core PCM Formula

For any sample rate, bit depth, and number of channels, that arithmetic is the core storage calculation.

• If a CD-like sample rate is 44,100 samples per second, and PCM records at 16 bits per sample, then the number of bytes per second for a stereo file is:

`` 44,100 × (16 ÷ 8) × 2 = 1,764,000 bytes ``

• When the bit depth goes up to 24 bits, this doubles the storage cost:

`` 44,100 × (24 ÷ 8) × 2 = 2,646,000 bytes for stereo 24-bit ``

• For a 48 kHz / 24-bit stereo audio master, the calculation is:

`` 48,000 × (24 ÷ 8) × 2 = 2,880,000 bytes ``

You can plug in the numbers for any setting - bit depth, sample rate, channels - to arrive at an hourly cost.

How Big Is Uncompressed Audio?

When you unwrap the formula, every byte is accounted for. And there are no shortcuts or reductions for common recording settings. Here is the space an hour of audio takes for standard PCM settings:

• A 48 kHz / 16-bit mono file is 345.6 MB
• At the same sample rate, 24-bit mono is 345.6 MB
• When the capture is 24-bit stereo, the number doubles to 1.04 GB per hour
• At 16 bit, the stereo hour is 317.52 MB

That is a lot of storage - and it only goes up from there. Moving to 96-kHz sampling adds another 100% for all of the above:

• 96 kHz / 24-bit mono is 1.0368 GB
• 96 kHz / 24-bit stereo is 2.0736 GB

The more increments you add, the faster the bytes multiply.

Lossy Formats Are Different

The to-the-byte arithmetic only works for straight PCM. Lossy formats like MP3, AAC, and Vorbis work differently. For these, storage is determined by the audio codec’s defined bitrate, not the sample rate of the recording. Bitrate and bit depth are entirely separate things.

For a compressed codec like MP3 or AAC, the encoder shrinks the original into a compressed bitstream that has a constant or target bitrate, such as 192 kbps. For these formats, the formula is simple:

• For lossy audio, the hourly cost in bytes is:

`` bytes = bitrate × 125 × duration (in seconds) ``

• So for a 128 kbps MP3, your formula is:

`` 128,000 × 125 × 3,600 = 57,600,000 ``

• Similarly, a 48 kbps AAC bitstream has:

`` 48,000 × 125 × 3,600 = 21,600,000 ``

Typical bitrates for MP3 or AAC delivery are:

• 48 kbps - Yields 21.6 MB
• 64 kbps - Yields 28.8 MB
• 128 kbps - Yields 57.6 MB
• 160 kbps - Yields 72 MB
• 192 kbps - Yields 86.4 MB
• 256 kbps - Yields 115.2 MB
• 320 kbps - Yields 144 MB

Audio codecs like OPUS and FLAC also compress, but they are not sized by bitrate. For these, you will need a different formula - and a proper source.

How To Plan For Podcast Storage

Most podcast projects don’t plan for 96 kHz / 24-bit sessions - or even 44.1 kHz / 16-bit masters. The main work is delivered at 128 kbps or lower, and the final archive copies are a smaller set of high-quality stereo files.

That means most podcast archives can be estimated with a model like this:

Collection of Multi-track Sessions: for a monthly archive, budget for 48 kHz / 24-bit audio to allow for session edits. This is close to 1 GB per hour of stereo, so a month of sessions is 240 hours × 1.04 GB = 249.6 GB.

Publication of Stereo MP3s or AACs: Eventually, the archive will deliver at PUBLISH BITRATE kbps, such as 128/192 kbps. One hour is then 192,000 × 125 = 57,600,000 bytes (57.4 MB). A month of published episodes is

Conclusion

Ultimately, the raw space an hour of audio uses is