Audio file size calculator

Enter the duration in seconds and the bitrate in kilobits per second, and the calculator returns a decimal megabyte estimate. It is useful for planning podcast uploads, music libraries, voice recordings, streaming downloads, and storage budgets before an encoder produces the final file. The calculation is deterministic, immediate, and based on the payload rate rather than a particular audio codec or container.

Turn duration and bitrate into a practical size estimate

Compressed audio is commonly described by a bitrate such as 64, 128, 192, or 320 kilobits per second. That rate says how much encoded audio data is produced during every second of playback. To estimate the complete payload, this calculator multiplies the duration in seconds by the target bitrate in kilobits per second. It then converts bits to bytes and uses decimal megabytes, where one megabyte is 1,000,000 bytes. In compact form, the calculation is duration multiplied by bitrate, divided by 8,000. The result is returned as file_size_mb and rounded to no more than six decimal places for stable, readable output. Use the total running time of the exported recording, including intros, outros, silence, and any other audio that remains in the finished program. Use the actual encoder target rather than the bitrate of an unrelated source file. With those two values, the estimate offers a clear baseline for upload limits, download planning, and storage forecasts before encoding begins.

Understand what the estimate includes and excludes

The result represents the nominal encoded audio payload at a constant target bitrate. A real file can differ slightly because containers may add headers, tags, artwork, chapter data, indexes, padding, or other metadata. Variable-bitrate encoding can differ more because the encoder spends additional bits on complex passages and fewer bits on simpler passages; its advertised bitrate is usually an average target rather than an exact rate for every second. Codec efficiency does not change this arithmetic: at the same bitrate and duration, MP3, AAC, Opus, and other compressed formats produce approximately the same payload size, although they may deliver different perceived quality. Uncompressed PCM audio is better estimated from sample rate, bit depth, channel count, and duration, not from a compressed target bitrate. The calculator deliberately uses decimal MB, which is common for network transfers and storage advertising. An operating system that reports binary MiB may display a smaller number for the same byte count. Treat the answer as a planning estimate, not a byte-exact promise about the final container.

Choose inputs that match your publishing workflow

Start with duration measured in seconds. Convert minutes by multiplying by 60, and include partial minutes when accuracy matters. Then choose the bitrate configured in the encoder or publishing preset. A speech-only recording may use a lower bitrate than stereo music, while an archival master may use a very different uncompressed format that this calculator is not intended to model. The service rejects zero, negative, missing, nonnumeric, infinite, and otherwise invalid values because none describes a meaningful duration or bitrate. For batch planning, call the API once per candidate or compute several scenarios in your own workflow: for example, compare the same episode at multiple target bitrates, or multiply the per-file estimate by the expected number of releases. Each API request costs $0.002, while the browser experience can perform the same deterministic calculation locally. When a platform enforces a strict maximum upload size, leave a safety margin for metadata and encoder variation instead of selecting settings whose estimate lands exactly on the limit.