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Video File-Size Calculator
Know roughly how large an export will be before you start an upload. This estimate uses your chosen average bitrate rather than guessing from resolution.
The calculation
File size in bytes = duration in seconds × (video Mbps × 1,000,000 + audio kbps × 1,000) ÷ 8. Decimal MB uses 1,000,000 bytes; binary MiB uses 1,048,576 bytes. Those labels are not interchangeable. Audio is included separately so a small soundtrack is not silently excluded.
Worked example: a one-minute edit
For 60 seconds at 10 Mbps video plus 128 kbps audio, the total bitrate is 10.128 Mbps. Multiply by 60 and divide by eight to obtain 75.96 MB, or about 72.44 MiB. This is an estimate of encoded stream size, not a promise that the finished MP4 will have exactly that byte count.
What this estimate cannot tell you
Container overhead, metadata and variable bitrate change the actual file size. A variable-bitrate encoder can use more data for detailed movement and less for simple scenes. If the bitrate you enter is a target or maximum rather than a measured average, the calculation inherits that uncertainty.
Resolution is not a file size
Two 4K files can have very different sizes because their duration, codec, bitrate and audio differ. Do not infer upload time or storage requirements from the word 4K alone. Read the file properties or your export settings and use those values here.
Before you upload
Keep your original files until the finished export has been downloaded and checked. Confirm the receiving service accepts the container and codec. A smaller export can be useful for sharing, but it should not automatically replace your camera original.
Frequently asked questions
Does changing the filename compress a video?
No. A filename or file extension does not change the encoded video. Compression requires re-encoding or another actual change to the media.
Why is the result different from my computer?
Your computer may use binary units while labelling them as GB, and the file may have a different average bitrate or additional metadata.
Formulas and examples reviewed on 26 October 2026. Planning estimates, not measurements of your footage or equipment.