Choose your fileChoose an MP3, WAV or other audio file. WAV files give the biggest savings, because they are not compressed.
Choose a target sizeType the size you need in MB, for example the limit of an email or a website, and press Fit to this size. The tool picks the best bitrate that fits.
Bitrate and monoA lower bitrate means a smaller file and lower quality: 128 kbps is a good balance for music and 64 kbps is enough for speech. Mono makes the file about half the size.
Sample rateLowering the sample rate also makes the file smaller, but it removes the high frequencies. 22,050 Hz and 16,000 Hz are enough for speech.
The result line shows the estimated size before you download. Compressing an MP3 again loses a little more quality, so keep your original file. For sample rates below 32,000 Hz MP3 allows at most 160 kbps: if you choose more, the tool lowers it for you and tells you the value it used.