What formula is used?

File size (bytes) = bitrate (kbps) × duration (seconds) ÷ 8 × 1000. Dividing by 8 converts bits to bytes; multiplying by 1000 converts kilobits to bits.

Why does the actual file size differ from the calculated result?

The calculation gives the raw audio data size. Real files also include a container header (ID3 tags, FLAC metadata, etc.) which adds a few kilobytes. For files longer than a minute the difference is under 1%.

What are common audio bitrates?

Typical MP3/AAC bitrates: 96 kbps (voice/podcast), 128 kbps (standard quality), 192 kbps (good quality), 256 kbps (high quality), 320 kbps (maximum MP3). Lossless formats like FLAC use 400–1400 kbps depending on sample rate and bit depth.

Does this work for lossless audio?

Yes. Enter the average bitrate of the lossless file (visible in your audio player or file properties) and the duration. FLAC uses variable bitrate, so use the average bitrate for an estimate.

What is the difference between kbps and KB/s?

kbps is kilobits per second (1 kbps = 1000 bits/s). KB/s is kilobytes per second. To convert: KB/s = kbps ÷ 8. A 128 kbps stream transfers 16 KB every second.

Audio Bitrate Calculator

Name: Audio Bitrate Calculator
Availability: InStock
Author: Nham Vu

Enter bitrate and duration to get file size, or enter target file size and duration to find the required bitrate.

Calculation Mode

Bitrate

kbps

Duration

Hours

Minutes

Seconds

Result

Fill in the fields and click Calculate

File Size

Bitrate Comparison (same duration)

Bitrate	File Size

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Summary

Enter bitrate and duration to get file size, or enter target file size and duration to find the required bitrate.

How it works

Choose a calculation mode: "Bitrate → File Size" or "File Size → Bitrate".
Enter the bitrate in kbps (kilobits per second).
Enter the audio duration using hours, minutes, and seconds fields.
Results update instantly as you type.
Use the copy button to copy the result to your clipboard.

Use cases

Estimate how large an MP3 or AAC podcast episode will be before encoding.
Find what bitrate to use when you have a strict file size limit for a platform.
Plan storage for a music library encoded at a specific bitrate.
Check how much space an audiobook will consume at different quality settings.
Compare file sizes across 128 kbps, 192 kbps, and 320 kbps for the same track.
Determine the bitrate needed to fit an album on a device with limited storage.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu