Audio file size calculator
Estimate a recording's file size from its format, bitrate, and length before you hit record — and see whether it fits cloud transcription limits like Whisper's 25 MB cap.
Recording parameters
Audio format
60 min at 128 kbps (MP3/M4A)
Size formula: duration × bitrate ÷ 8. Real files vary slightly with encoder overhead and metadata. Manual transcription estimate uses the industry 4–5× realtime rule for a trained typist.
Stop Recording, Uploading, and Splitting. Speak Once.
Cloud transcription APIs like OpenAI's Whisper enforce strict 25 MB upload limits. As the calculator shows, a standard 1-hour recording at 128 kbps is already over 56 MB — so the usual workflow becomes: record, download, compress with FFmpeg, split into chunks, upload each piece, and stitch the text back together. Then someone still has to proofread it.
The whole pipeline exists because the words were trapped in an audio file in the first place. CoScript removes the file: its speech engine runs locally on your Windows PC and turns your voice into clean, AI-formatted text while you speak, pasting it straight into any app.
- No audio files to store, compress, or upload — nothing leaves your machine.
- No 25 MB caps, per-minute API fees, or chunking scripts.
- No 4–5× realtime transcription backlog — the text is done when you stop talking.
When you do need to estimate audio size
For podcasts, interviews, and archival recordings, the math above holds: file size = duration × bitrate ÷ 8. Voice recordings stay clear down to 64 kbps mono, which is the cheapest way to fit longer recordings under upload limits without re-encoding later.
Stop typing. Start talking.
CoScript turns your voice into clean, AI-formatted text and pastes it straight into any Windows app at up to 200 words per minute — offline engine, 100+ languages, 30+ writing tones. Free to start.