How to Calculate Audio File Size and Bitrate Storage Needs
Audio file sizes follow from arithmetic, which means they can be worked out in advance rather than discovered after a long export. This page is that arithmetic, and it needs no file: you are planning something that does not exist yet. For lossy formats the calculation is exact and simple. A bitrate is bits per second, so multiply it by the duration and divide by eight for bytes. Three and a half minutes at 192 kbps is about 5 MB, every time, because constant bitrate encoding means what it says. For uncompressed WAV the arithmetic is equally direct: sample rate times channels times bytes per sample times duration. At 44.1 kHz, stereo, 16-bit, that is 176,400 bytes a second, or roughly 10 MB a minute. Switching to 24-bit multiplies by 1.5, and switching to mono halves it. Seeing those two levers next to each other is often the point of the exercise. FLAC is the one figure that is an estimate rather than a calculation, and the page is explicit about it. Lossless compression depends on the audio: a sparse solo recording compresses further than a dense loud master, because prediction works better on predictable material. Around 55 percent of the uncompressed size is a reasonable planning figure, and your actual files will land somewhere either side of it. The per-hour rate is shown alongside, which is the number you want when the question is about storage rather than a single file. Recording eight hours a week in 24-bit stereo WAV is a different proposition from doing it in mono FLAC, and the difference over a year is worth knowing before you start rather than when the disk fills up.
How to Use the Audio369 Online File Size Calculator (Step-by-Step)
From half a minute to three hours. No file is needed, since this calculates from the settings rather than measuring anything.
MP3, AAC or M4A, WAV at 16 or 24 bits, or FLAC. Bitrate applies to the lossy ones; sample rate and channels to the rest.
Bitrate from 32 to 320 kbps for lossy; sample rate and mono or stereo for uncompressed. Each one moves the total predictably.
The size answers a question about one file, the per-hour rate answers a question about storage across many.
Technical Architecture & Audio Engine Specifications
One hour of audio, by format
| Format | One hour | Notes |
|---|---|---|
| MP3 128 kbps | ✓ About 58 MB | The usual podcast size |
| MP3 320 kbps | ✓ About 144 MB | Transparent, and two and a half times larger |
| WAV 16-bit stereo 44.1 | ✓ About 635 MB | Uncompressed; the arithmetic is fixed |
| WAV 24-bit stereo 48 | ✓ About 1 GB | Studio delivery, and it shows |
| FLAC from 16-bit | ✓ About 350 MB | An estimate; depends on the material |
Who Uses Audio369 File Size Calculator? (Practical Creative Workflows)
Choosing a bitrate to fit a limit
Work backwards from the cap you were given instead of exporting at a guess and finding out afterwards.
Planning storage for a project
A season of episodes recorded in WAV needs a number before it needs a disk, and the per-hour rate gives you it.
Budgeting hosting bandwidth
File size multiplied by expected downloads is the whole of a hosting bill, and halving the bitrate halves it.
Deciding between formats
Seeing FLAC and WAV side by side for the same material makes the archiving decision obvious in a way description does not.
Explaining a size difference
When somebody asks why a five-minute file is 50 MB, the formula is the answer, and it is easier to show than to describe.
Frequently Asked Questions (FAQ)
Why is the FLAC figure an estimate? +
Because lossless compression depends on the audio itself. Quiet, sparse material compresses further than dense, loud material. 55 percent of the uncompressed size is a fair planning figure rather than a guarantee.
Do I need to upload a file? +
No, and there is nowhere to. This calculates from the settings you choose, which is what makes it useful before the audio exists.
Why is my actual MP3 slightly different from the prediction? +
Tags, cover art and encoder padding all add a little. The audio stream itself matches the calculation; the file around it carries a small overhead.
Does doubling the sample rate double the size? +
For uncompressed formats, yes, exactly. For lossy formats it does not, because the bitrate you set is the budget regardless of the sample rate.
How much does mono save? +
Half, for uncompressed audio, and close to half for lossy at the same bitrate. It is the single largest saving available on speech recordings.
What is the mathematical formula for uncompressed audio file size? +
Size equals sample rate multiplied by bit depth, number of channels, and duration in seconds, divided by 8 to convert bits into bytes. At 44.1 kHz 16-bit stereo, audio consumes approximately 10.1 MB per minute.
How much disk space does 24-bit 96 kHz studio audio require? +
A 24-bit 96 kHz stereo WAV recording generates 4608 kbps of uncompressed data, which equals approximately 34.5 MB per minute or over 2 GB per hour per stereo track.
How much bandwidth does converting to mono save on spoken audio? +
Because mono contains only a single channel of audio data, converting stereo voice recordings to mono reduces uncompressed file size by exactly 50% without altering voice fidelity.