Free tool · runs in your browser

Video Duration from File Size Calculator

Tell the calculator your file-size budget, video bitrate, and audio bitrate — it returns the maximum HH:MM:SS you can fit. The inverse of the file-size calculator.

Maximum duration

00:04:40

≈ 4.7 minutes at 8.192 Mbps combined (8 Mbps video + 192 kbps audio). 287.0 MB budget.

How to use this tool

  1. 01

    Enter your target file size

    The platform limit or storage cap.

  2. 02

    Enter the bitrate you'd encode at

    Lower bitrate = longer possible duration.

  3. 03

    Plan or compress

    Use the result to plan content length, or use Video Compressor to fit existing footage.

Why this matters

Hitting an upload limit with a finished export is one of the most frustrating moments in any video workflow — the render time is already spent, and now you either re-encode at a worse bitrate or trim and re-export. Solving the problem backwards from the size cap lets you cut at the right place the first time, pick a lower bitrate intentionally rather than letting the encoder make the call, or know up front that a 30-minute talking-head won't fit a TikTok upload no matter what you do.

This calculator keeps the math transparent — file size in MB or GB, separate video and audio bitrate inputs, HH:MM:SS output — and uses the same combined-bitrate formula as the Video File Size Calculator so the two tools agree by construction. When you actually need to fit existing footage under a hard cap, the Video Compressor can target a final size directly without you having to back-solve a bitrate.

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FAQ

Any time you have a hard size cap and need to know how much footage fits inside it — WhatsApp's 64 MB per-clip limit, a 25 MB email attachment, a client portal that refuses anything over 500 MB, a TikTok 287 MB ceiling, or simply an SD-card capacity during a long shoot. Knowing the maximum duration before you start recording or trimming lets you plan content length up front instead of discovering the problem mid-export. It's the inverse of the file-size calculator — same formula, solved for time instead of bytes.

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