MP3 Bitrate Calculator (Free)
Estimate MP3 size by duration and bitrate
Enter duration and bitrate to estimate MP3 size, or set a target size to get a suggested bitrate. Perfect for WhatsApp voice notes, podcasts and music. Works great with our MP3 trimmer and compressor.
By default: size = (bitrate × duration) / 8 (MP3 CBR = total bitrate). If “per-channel” is enabled, size = (bitrate × channels × duration) / 8.
Hit a size limit
If you have a MB cap (email, messengers, car USB), compute the target bitrate and export.
Trim before compressing
Remove silence to keep more quality at the same size. Open trimmer.
Compress with control
Use our MP3 compressor to reach your final size while preserving clarity.
Which bitrate should I choose for voice or music?
For voice (WhatsApp notes, interviews), 64–128 kbps is typically fine. For music, 128–192 kbps is a balanced range. 320 kbps is often unnecessary unless you really need it.
If your goal is a smaller file, first trim what you don’t need and then compress. You can also merge audios for compilations.
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FAQ
How is MP3 size estimated?
We assume constant bitrate: size ≈ (bitrate × duration) / 8. Actual files may vary slightly due to headers and encoder settings.
What bitrate should I use?
Voice: 64–128 kbps is usually fine. Music: 128–192 kbps is a safe range; 320 kbps is often unnecessary.
Trim before compressing?
Yes. Trimming silence preserves more quality for the same final size. Open the MP3 trimmer.