Video Size Calculator
Estimate compressed video file size from duration, resolution bitrate presets, and audio bitrate.
How Video File Size Is Calculated
Compressed video file size depends on how many bits are stored per second (bitrate) and how long the clip runs. Add the video and audio bitrates, multiply by duration, then convert kilobits to megabytes.
Video Size Formula
$$\text{Size (MB)} = \frac{(\text{video kbps} + \text{audio kbps}) \times \text{duration (s)}}{8 \times 1024}$$Example: 8,000 kbps video + 128 kbps audio for 60 seconds gives \((8128 \times 60) / 8192 \approx 59.5\) MB.
Typical Bitrate Presets
720p H.264 often lands near 5 Mbps, 1080p near 8 Mbps, and 4K near 35 Mbps depending on codec and content. Use custom bitrate when you know your encoder settings.
Related tools: Audio File Size Calculator and Download Time Calculator.
Frequently Asked Questions
Why divide by 8 and 1024?
Bitrate is in kilobits per second. Divide by 8 to get kilobytes, then divide by 1024 to convert kilobytes to megabytes.
Does this include container overhead?
No. This estimates payload size from bitrate. MP4/MKV headers and metadata add a small amount on top.
Are the resolution presets exact?
They are practical defaults. Real file size varies with codec (H.264, HEVC, AV1), frame rate, and scene complexity.
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