MP3 Compressor

Make an MP3 smaller by saving it at a lower bitrate. You see the new size before you start, and the file is compressed in your browser, never sent to a server.

Files Stay on Your Device

Drop the MP3 you want smaller

Compresses MP3 to 64, 96, 128 or 192 kbps. Also works on M4A, WAV and other audio files. It stays on your device.

Choose a File

Your browser converts the file. Nothing is sent to a server.

  • No signup, no watermark
  • Converts on your device
  • About 2 sec for a 47 sec clip
  • Works offline once loaded

How to Compress an MP3 File

  1. 1

    Choose Your MP3

    Choose the MP3. Drop it on the page, tap Choose a File, or paste a direct link to the file.

  2. 2

    Pick a Smaller Bitrate

    Pick a lower bitrate. Each option shows about how big the new MP3 will be. 96 kbps is selected; choose 64 kbps for the smallest voice files, 128 kbps for music. Turn on Trim to cut it shorter as well.

  3. 3

    Compress and Download

    Press Convert to MP3. Compare the new size on the Download button with the original, play it in the preview, and download it.

How MP3 Compression Works

The size of an MP3 depends on two things: its length and its bitrate. Bitrate is how many kilobits each second of sound uses. Halve the bitrate and the file is about half the size.

This compressor decodes the MP3 and saves it again at the bitrate you pick. A 320 kbps song saved at 96 kbps becomes about 70% smaller. Cutting off the parts you do not need with Trim makes it smaller still.

What the MP3 compressor doesAn MP3 at 320 kbps on the left holds about 2.4 megabytes of audio a minute. An arrow labelled decode audio, encode at a lower kbps points to a smaller MP3 on the right at 64, 96, 128 or 192 kbps; at 96 kbps it is about 0.72 megabytes a minute.MP3 at 320 kbpsAudio, about 2.4 MB a minute · decodeddecode audioencode at lower kbpsSmaller MP364, 96, 128 or 192 kbps96 kbps: about 0.72 MB a minuteWhat the MP3 compressor doesMP3 at 320 kbpsAudio, about 2.4 MB a minute · decodeddecode audioencode at lower kbpsSmaller MP364, 96, 128 or 192 kbps96 kbps: about 0.72 MB a minute
Compression here means saving the same sound again at a lower bitrate.
MP3 size for each minute of sound
BitrateSize per minuteGood for
64 kbpsAbout 0.5 MBVoice notes, lectures, audiobooks
96 kbpsAbout 0.7 MBPodcasts, interviews, phone listening
128 kbpsAbout 1 MBMusic when size matters
192 kbpsAbout 1.4 MBMusic with little audible loss
320 kbpsAbout 2.4 MBThe largest MP3, the most detail

Why Compress an MP3

  • Fit Under an Upload Limit

    Email, school portals, job sites and forms often cap file size. Gmail stops attachments at 25 MB, which a long 320 kbps recording can pass.

  • Send It Faster

    A smaller MP3 sends faster on WhatsApp or Telegram and uses less mobile data for you and the person you send it to.

  • Save Phone Storage

    Lectures, audiobooks and voice recordings sound fine at 64 or 96 kbps, which takes a third to half the space of a 192 kbps copy.

When Compressing Will Not Help

An MP3 that is already at a low bitrate will not get smaller. Saving a 96 kbps MP3 at 96 kbps or higher gives a file the same size or bigger. Pick a lower bitrate than the original, or use Trim to keep only part of it.

Each time an MP3 is saved again it loses a little detail. Speech stays clear at 64 kbps, but for music 96 kbps is about as low as most people will want to go.

Make an MP3 Fit Under a Size Limit

Upload forms and attachments often stop at 16 MB or 25 MB. How long an MP3 can be under a limit depends only on its bitrate.

Minutes of MP3 that fit in 16 MB

  • 64 kbpsAbout 33 minutes
  • 96 kbpsAbout 22 minutes
  • 128 kbpsAbout 16 minutes
  • 192 kbpsAbout 11 minutes
Minutes = limit in MB x 8,000 / kbps / 60, with 1 MB = 1,000,000 bytes.
Longest MP3 that fits under two common limits
BitrateUnder 16 MBUnder 25 MB (Gmail attachments)
64 kbpsAbout 33 minutesAbout 52 minutes
96 kbpsAbout 22 minutesAbout 34 minutes
128 kbpsAbout 16 minutesAbout 26 minutes
192 kbpsAbout 11 minutesAbout 17 minutes

Leave a little room below the limit, because some services count a megabyte as 1,048,576 bytes. If a recording is still too long, turn on Trim and keep only the part you need.

What Changes Inside the File

At 128 and 192 kbps the sound keeps its sample rate and is simply encoded with fewer bits. At 96 kbps it is first resampled to 32 kHz, and at 64 kbps to 24 kHz.

Resampling removes only the highest frequencies, above about 16 kHz at 96 kbps and 12 kHz at 64 kbps. Speech sits far below that, so voices stay clear, while the encoder spends its smaller budget on the sound you can hear instead of on hiss.

MP3 Compressor: Frequently Asked Questions

How do I reduce the size of an MP3 file?
Choose the MP3 here, pick a lower bitrate such as 96 or 64 kbps, and press Convert to MP3. Each option shows about how big the result will be.
How much smaller will my MP3 get?
It depends on the original bitrate. A 320 kbps MP3 saved at 96 kbps is about 70% smaller; a 128 kbps MP3 saved at 64 kbps is about half the size.
Is my MP3 file sent to a server?
No. Your browser reads the MP3 file and writes the MP3 on your own device. Nothing is sent to MP4toMP3.io or anyone else, and the page keeps working with Wi-Fi off once it has loaded.
Does compressing an MP3 lower the quality?
Yes, a little, because the sound is encoded again at a lower bitrate. Speech stays clear even at 64 kbps; music starts to sound duller below 96 kbps.
Why did my MP3 not get smaller?
Because the original already had a bitrate at or below the one you picked. Choose a lower bitrate, or trim the file to a shorter part.
Can I compress M4A, WAV or other audio files too?
Yes. Any audio file your browser can play is saved as a smaller MP3 the same way. A WAV file usually shrinks by more than 90%.
How do I compress an MP3 for email?
Pick a bitrate that brings the file under the limit; Gmail allows 25 MB. At 96 kbps about 34 minutes fit; at 64 kbps about 52 minutes. The size estimate under each option shows the result before you start.
How do I get an MP3 under 16 MB?
Choose 96 kbps for up to about 22 minutes, or 64 kbps for up to about 33 minutes. For anything longer, use Trim as well.
Can I compress an MP3 on my phone?
Yes. Open this page in Chrome on Android or Safari on iPhone, choose the MP3 from Files, pick a bitrate and download the smaller copy.
Is the MP3 compressor free?
Yes. There is no account, no watermark and no paid plan. The conversion runs on your own device, so there is no server cost to pass on.
Can I compress several MP3 files at once?
Not yet. Compress one file at a time; each takes a few seconds. Batch compression is planned.

Ready to Compress Your MP3?

Choose a file at the top. It is free, private and done in your browser in a few seconds.

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