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Video file-size calculator
Estimate how big a video export will be before you render it. Enter the bitrate and length, or pick a resolution preset to fill in a typical bitrate, and the size updates instantly.
It assumes a constant bitrate, so a variable-bitrate export on busy footage can run a little larger. Close enough to know whether it will fit under a platform's upload cap or an email attachment limit.
Frequently asked questions
How do you calculate video file size?
File size equals bitrate multiplied by duration. A bitrate in megabits per second times the length in seconds gives megabits, then dividing by 8 gives megabytes. Higher bitrate or longer video means a bigger file.
What bitrate should I export at?
As a rough guide for H.264: about 5 Mbps for 720p, 10 Mbps for 1080p, 20 Mbps for 1440p and 45 Mbps for 4K. Double it for 60fps footage. Higher bitrate looks better but makes a larger file, so match it to where the video is going.
Why is my export bigger than this estimate?
The estimate assumes a constant bitrate. Many encoders use variable bitrate, which can run higher on complex, fast-moving footage. Audio adds a little too. Treat the figure as a close approximation, not an exact size.
Is this calculator free?
Yes. It runs entirely in your browser with no account and nothing uploaded. It is a free tool from FileFlippers.
Ready to send it?
FileFlippers sends large files to clients and collaborators on one link, with watermarked previews and payment-gated delivery. Free to start, no card required.