How to Reduce the File Size of an MP3 or Recording

Sometimes a recording or song is too big to attach to an email, or your storage is full. Here's how audio file size works and how to bring it down.

Three things decide the size

How to reduce it

1. Add your file to the Audio Converter.
2. Choose MP3 and lower the quality (bitrate). For speech, 128 kbps is a good choice; for music, around 192 kbps.
3. Lower the sample rate to 16,000 to 22,050 Hz. That's plenty to understand a human voice.
4. If it was recorded in stereo, check "Convert to mono". The file shrinks by almost half.
5. Save and check the new size.

Speech and music need different settings

Files that only contain speech, like phone calls or meeting recordings, stay perfectly understandable even when you shrink them a lot. At 128 kbps, 16,000 to 22,050 Hz and mono, they can get close to one tenth of the original size. Music files, on the other hand, start to sound worse if you go too low, so keep them at 192 kbps or higher and 44,100 Hz.

Cut it down to shrink it further

If there are parts at the start or end you don't need, keep only what matters with the MP3 Cutter first. The file gets smaller in proportion to the time you remove. To keep several recordings together, join them with Merge MP3 and reduce the size once at the end.

A rough idea of how much it shrinks

For example, a 10-minute stereo recording kept as uncompressed audio is about 100 MB. Converted to 128 kbps, mono, 22,050 Hz, it often ends up under 10 MB. The actual savings depend on the original file.

Good to know

• Re-saving an MP3 at a lower bitrate compresses it twice, which lowers quality more. If you can, start from the original (WAV or a high-quality file).
• Going extremely low (64 kbps or less) can make even speech sound mushy.
• If you add a video, only its audio track is extracted automatically.
• The converter can process several files at once and give you a ZIP.

If an email attachment limit is the problem

Many email services, including Gmail and Outlook, limit attachments to around 20 to 25 MB. For a long call or lecture recording, go down to 128 kbps, mono, 22,050 Hz with the steps above. If it's still too big, cut out just the part you need. You can also share a cloud link, but a small file the recipient can open right away is often more convenient.

Common problems

• The file barely got smaller: the original may already be at a low bitrate. Check its bitrate before converting.
• It sounds muffled: sample rates that are too low (8,000 Hz or less) cut off high frequencies. Stay at 16,000 Hz or higher.
• Does this work for videos too? Yes. Add an MP4 or other video and the audio track is extracted, then reduced the same way.

Sources and date checked

Checked: October 6, 2026

• Wikipedia, Bit rate — https://en.wikipedia.org/wiki/Bit_rate
• Wikipedia, MP3 — https://en.wikipedia.org/wiki/MP3

This article is general information. Results depend on the original file.

Frequently asked questions