OPUS to MP3 Converter

Opus is the audio codec of WhatsApp and Telegram voice messages, Discord, and many web recordings. It sounds good at very low bitrates, but many players, editors and transcription services still ask for MP3. This converter turns .opus, .ogg and .webm Opus files into MP3 in your browser, so private voice messages are never uploaded anywhere.

How to use this tool

1. Save the voice message or Opus file to your device (in WhatsApp: share or export the audio).
2. Choose one or more .opus, .ogg or .webm files.
3. Keep 96 kbps for voice, or choose 192 kbps for music.
4. Press Calculate and download the MP3s.

Formula

MP3 size (bytes) ≈ bitrate (kbps) × 1000 ÷ 8 × length (s)

Opus always plays at 48 kHz, so the MP3 is made at 48 kHz too, except stereo at 96 kbps or less, where LAME switches to a lower rate (32 kHz at 96 kbps) and the result says so. Chrome, Edge and Firefox decode Opus themselves and LAME writes the MP3, so no download is needed; when the browser cannot (some Safari versions), the ffmpeg engine is used (about 30 MB, downloaded once). Voice messages are mono, and "Keep" leaves them mono, which halves the size.

Example

A 2-minute WhatsApp voice message is about 0.4 MB as Opus (around 24 kbps). At 96 kbps mono the MP3 is 96,000 ÷ 8 × 120 = 1.44 MB; at 64 kbps it would be 0.96 MB.