Free online WAV to GSM converter

A telephone system, voicemail application, or legacy speech program may require GSM audio instead of standard PCM WAV. Converting produces the low-bitrate speech format those systems accept, but it is intended for voice rather than music.

What the WAV format is

WAV is a RIFF-based audio container that commonly stores uncompressed PCM samples. Windows recording utilities, Audacity, digital audio workstations, recording hardware, and other capture software use it because PCM preserves the source recording without codec loss. CD-quality stereo PCM uses about 1.4 Mb/s, so WAV files are relatively large.

What the GSM format is

GSM audio normally means the GSM 06.10 full-rate speech codec, not the cellular network itself. It compresses mono speech to approximately 13.2 kbps, making it suitable for voicemail, telephony software, PBX systems, and older speech applications that accept .gsm files.

A standard GSM 06.10 output uses 8,000 Hz, one channel, and 16-bit PCM as its decoded audio characteristics. It is much smaller than PCM WAV, but the compression is lossy and generally unsuitable for music, sound effects, or extensive further editing.

How to convert WAV to GSM

For a conversion without installing software, use the converter on 101convert.com: select the WAV file, choose GSM as the output format, start processing, and download the resulting file.

For local conversion or batch processing, FFmpeg can resample and encode the file in one command:

ffmpeg -i input.wav -ar 8000 -ac 1 -c:a gsm output.gsm

-ar 8000 sets the sample rate to 8 kHz, -ac 1 downmixes the audio to mono, and -c:a gsm selects the GSM 06.10 encoder. Replace the input and output filenames as needed. Check the result with:

ffprobe output.gsm

SoX can perform the same conversion when its GSM format support is available:

sox input.wav -r 8000 -c 1 output.gsm

Some applications require GSM-encoded audio inside a WAV container rather than a raw .gsm file. Create that variant with:

ffmpeg -i input.wav -ar 8000 -ac 1 -c:a gsm output-gsm.wav

Quality and compatibility limits

GSM 06.10 is optimized for intelligible speech and can produce metallic or muffled artifacts, especially with music, background noise, and rapidly changing sounds. An input that is already 8 kHz mono avoids additional resampling, but it does not prevent the codec's lossy compression.

The .gsm extension does not identify every technical requirement. Confirm whether the receiving application expects raw GSM 06.10 frames, GSM audio in a WAV container, or a different codec such as GSM-EFR. Sample rate, channel count, container, codec, and frame format must all match the destination application's specification.