Audio to MP3 conversion guide
Learn how bitrate, channels, sample rate and peak adjustment affect MP3 conversion and file size.
Select a file
Select one audio file at a time. Input is limited to 50 MiB and 10 minutes, and your browser must be able to decode it using Web Audio API. You can also use the generated six-second sample.
Choose output settings
The presets are 64kbps mono at 22.05kHz, 128kbps stereo at 44.1kHz and 192kbps stereo at 44.1kHz. Custom settings let you choose bitrate, channels and sample rate. At 22.05kHz the maximum bitrate is 160kbps; the other selectable sample rates support up to 320kbps.
Source and decoded sample rates
The app reads source sample rates from supported WAV and MP3 headers. For other formats it explicitly shows the decoded sample rate. Browser decoding can resample audio, so source and processing rates can differ.
Peak adjustment
After resampling and channel conversion, peak adjustment applies one gain value to the whole file toward about -1dBFS before encoding. Gain increases are capped at 20dB. It does not raise quiet sections separately or normalize to a LUFS target. The decoded MP3 peak may differ after lossy encoding.
Compare file sizes
MP3 uses lossy compression. Estimated size is an approximation based on duration and bitrate; actual output includes frame overhead. An already small source may produce a larger result. Mono does not halve size at the same MP3 bitrate.
Listen and download
Play the original and converted audio, check the actual size, then download the MP3. Change settings lets you convert the same original again with different settings.
Processing scope
Decoded PCM is limited to 256 MiB. Smaller files may still fail if the device lacks memory. Format support depends on the browser and codec.