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Video Bitrate & File Size Calculator

Math

Calculate the video file size from a target bitrate and duration, or the required bitrate to hit a target file size, with an optional separate audio bitrate.

Video bitrate and file size are directly proportional to each other at a fixed duration, and this tool works the conversion either direction. Give it a video bitrate, an optional audio bitrate, and a duration to see the resulting file size, which is the question you're asking when picking an export setting. Or give it a target file size, like a platform's upload cap or a fixed amount of storage, and a duration to get the bitrate that hits it exactly, holding the audio track's bitrate fixed and solving for video. Everything is plain arithmetic over the numbers you supply: it reads no file and decodes nothing, so it can't tell you the real bitrate of an existing video, only what a given combination of numbers works out to.

videobitratefilesizecalculatorstreamingencodingupload

How to use Video Bitrate & File Size Calculator

  • 1.Pick a direction: bitrate to file size, or file size to bitrate.
  • 2.Enter the duration in seconds, plus the video bitrate (or target file size) and an optional audio bitrate in kbps.
  • 3.Read the resulting file size in both decimal MB and binary MiB, or the required video bitrate.

Frequently asked questions

What's the difference between MB and MiB in the result?
MB here is decimal (1 MB = 1,000,000 bytes), the convention bitrates and most upload-limit copy use. MiB is binary (1 MiB = 1,048,576 bytes), which is what macOS Finder, Windows Explorer, and most file managers actually display as a file's size, so the two numbers can differ by a few percent for the same file.
Can this read the bitrate of a video file I already have?
No. This is a pure calculator over numbers you type in; it doesn't parse any video file. For reading an existing file's actual bitrate you'd need a container/metadata reader, which is a different kind of tool.
How is the audio bitrate handled?
It's added to (or subtracted from) the video bitrate to get the total. In "file size to bitrate" mode, the audio bitrate is held fixed and only the video bitrate is solved for; if the audio bitrate alone would exceed the total bitrate available at your target size, the tool reports an error instead of a negative video bitrate.
Does this account for container overhead (MP4/MKV headers, index tables)?
No, the formula is exactly bitrate times duration divided by 8. Container overhead is typically well under 1% of the payload for anything longer than a few seconds, so this is a close estimate, not an exact prediction of the file an encoder will produce.

Use via API, SDK, or MCP

cURL# Free: 1,000 req/day · Pro: 10,000 req/day
curl -X POST https://api.utilix.tech/v1/tools/video-bitrate-calculator \
  -H "Authorization: Bearer utx_live_..." \
  -H "Content-Type: application/json" \
  -d '{"mode":"size-from-bitrate","durationSeconds":600,"videoBitrateKbps":5000,"audioBitrateKbps":192}'

Get an API key from your dashboard · Full API docs →

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