Free online ULAW to MP3 converter

Telephony systems often save recordings as ULAW, while many editors and sharing platforms accept MP3 but not raw ULAW files. Converting the recording makes it easier to play, edit, or share in those tools.

What ULAW is

ULAW usually refers to G.711 μ-law, an 8-bit companded audio encoding used in telephone systems and PBX recordings. A .ulaw file is often raw audio without a header, so its sample rate and channel count may not be stored in the file; 8 kHz mono is common.

What MP3 is

MP3 is a lossy audio format supported by most media players, phones, and audio editors. Its broad compatibility is useful for sharing, and a suitably low bitrate can reduce file size; the result depends on the chosen settings and source.

Convert online on 101convert.com

1. Open the ULAW-to-MP3 converter page and upload the file. You can add several files for batch conversion; the per-file size limit is shown on the page.
2. Before converting, set the bitrate, sample rate, and channels as needed.
3. Convert the file and download the MP3.

The page’s converter uses FFmpeg.

Convert offline with desktop software

FFmpeg is free, open-source command-line software for Windows, macOS, and Linux. For a headerless 8 kHz mono file, run:

ffmpeg -f mulaw -ar 8000 -ac 1 -i input.ulaw -ar 44100 -c:a libmp3lame -b:a 64k output.mp3

Change the input -ar and -ac values to the source’s actual sample rate and channel count; incorrect values can make the audio play at the wrong speed or sound distorted. The output -ar 44100 resamples to a widely supported MP3 rate but does not add source detail. If the audio is in a container that FFmpeg can identify, use its input detection instead of specifying raw μ-law parameters.

Quality and compatibility

G.711 μ-law recordings are already quantized and are commonly narrowband telephone audio. MP3 adds lossy compression and cannot restore missing frequencies or detail. Resampling or converting mono to stereo does not improve the source, and MP3 compatibility can vary with unusual sample rates or bitrates.