MP3 Compressor lowers the bitrate of an MP3 so the file gets smaller: for email attachments, chat apps, upload limits or a full phone. It runs in your browser, so the MP3 never leaves your device, and the result is a normal MP3 that plays everywhere.
How big is an MP3?
An MP3’s size depends only on its bitrate and its length, not on what is in it. That makes it easy to predict:
| Bitrate | Per minute | 1 hour |
|---|---|---|
| 320 kbit/s | 2.4 MB | 144 MB |
| 192 kbit/s | 1.4 MB | 86 MB |
| 128 kbit/s | 0.96 MB | 58 MB |
| 96 kbit/s | 0.72 MB | 43 MB |
| 64 kbit/s | 0.48 MB | 29 MB |
| 32 kbit/s | 0.24 MB | 14 MB |
To estimate the bitrate of your file, divide its size by its length: a 9.6 MB file that lasts 10 minutes is about 128 kbit/s. The tool shows the length and size as soon as you choose the file.
Which setting for which MP3
- Song or album track: Smaller (96 kbit/s). Music still sounds fine on phones and earbuds; cymbals and applause start to sound swirly below that.
- Podcast, lecture, audiobook: Small (64 kbit/s), with Mono ticked. Voices stay clear and an hour fits in about 29 MB.
- Voice note or meeting: Smallest (32 kbit/s, mono). About 14 MB per hour.
- A hard limit (an email server, a form, a chat app): Target file size. Type the limit in MB and the bitrate is worked out for you.
Tips
- Compress from the original file. An MP3 that has been compressed several times collects artefacts each time.
- Lowering the bitrate is the only way to make an MP3 noticeably smaller. Mono halves the data needed for the same sound, which is why mono speech at 64 kbit/s sounds better than stereo speech at 64 kbit/s.
- If you need to go smaller than MP3 sounds good at, save as OGG / Opus or M4A instead, if the person or site you send it to accepts those.
- For a long recording that will not fit even at the smallest size, cut it into parts with the Audio Cutter first.