Video File Size Calculator
File size from bitrate and duration — or the bitrate a size budget allows.
Enter values
Mbps
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Step by step
The formula
size (MB) = bitrate (Mbps) × seconds ÷ 8
Video size is bitrate multiplied by time. Bitrate is how much data each second of video is allowed, so it controls quality directly — and because it is quoted in megabits while files are measured in megabytes, the conversion needs a division by eight.
All calculations run locally in your browser and update instantly as you type.
Example calculations
Common questions this calculator answers — select one to load its values.
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Frequently asked questions
What bitrate should I use?+
Rough guides for H.264: about 5 Mbps for 1080p30, 8 Mbps for 1080p60, 35–45 Mbps for 4K. Newer codecs such as H.265 or AV1 reach similar quality at roughly half the bitrate.
Why is my actual file a different size?+
Most encoders use variable bitrate, so quiet, still scenes use less data than fast action. This gives the average — treat it as a planning estimate rather than an exact figure. Audio tracks add a little more.
All calculations run locally in your browser. Nothing you type is sent to a server.