Work out how long a track runs from its file size and bitrate — or drop in a real file to read its exact duration.
The Audio Duration Calculator works out how long a recording is from its file size and bitrate — or, for uncompressed audio, from sample rate, bit depth and channels. It is handy when a file has no metadata, when you are budgeting storage or when you want to estimate how much audio fits in a given size.
Rounding is handled correctly (a duration is never displayed as “1:60”), and a data-rate card shows bytes per second and per hour.
duration = size × 8 ÷ bitrate. For PCM, bitrate = sample rate × bit depth × channels, e.g. 44,100 × 16 × 2 = 1,411,200 bps. Compressed files assume constant bitrate; variable-bitrate files and embedded tags make real durations differ by a few percent.
Estimate length from size.
How much audio fits in a given size.
Check recordings are complete.
Confirm a converted file is the right length.
| Modes | Compressed (kbps) and PCM (rate × bits × channels) |
|---|---|
| Output | h:mm:ss, minutes, seconds, data rate |
| Fill from file | Reads real duration/size |
About 10.4 minutes at 128 kbps and 4.2 minutes at 320 kbps.
About 9.4 minutes of CD-quality stereo.
The calculator assumes a constant bitrate. Real MP3 files often use variable bitrate encoding, which can shift the actual duration slightly from a flat calculation.
This tool runs entirely in your browser using the Web Audio API. Nothing is uploaded, stored or shared — there is no server to send your file to, so it works offline once the page has loaded.
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