Video file size calculator
Recording size from video and audio bitrate — in gigabytes and mebibytes.
Fill in the fields and the result will appear here automatically.
Estimate the supplied video and audio streams from their mean bitrates and duration. Rates are first converted to one scale and added, then bits are converted to bytes. The output uses decimal GB/MB and binary MiB. These are different representations of one volume; operating-system display behaviour is not part of the model.
How it works
Formula and logic
Total bitrate in bit/s = videoMbps·10⁶ + audioKbps·10³. Bytes = total bitrate·minutes·60/8. GB=10⁹ bytes, MB=10⁶ bytes and MiB=2²⁰ bytes; the binary row is MiB, not GiB. Video rate and duration are positive; audio may be 0 for a silent recording. For VBR use average rates over the same duration. Container data and extra tracks are not added automatically.
Example
Ten minutes at 8 Mbit/s video and 128 kbit/s audio takes 0.6096 GB, shown as 581.36 MiB in Explorer.
Fields and units
- Mean video bitrate — Mbit/s
- Mean audio bitrate — kbit/s
- Length — min
How to use
- — Enter the video bitrate — it is set in the camera or the encoder.
- — Enter the audio bitrate, usually between 96 and 320 kbit/s.
- — Enter the length of the recording in minutes.
- — Compare gigabytes with mebibytes if you are checking against Explorer.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- NIST: decimal and binary prefixes
- Limitation
- Mean total-bitrate model for the supplied audio/video streams. It does not select codec or quality and does not automatically include container data, subtitles or extra tracks.
FAQ
Why does the size differ from what Explorer shows?
Windows treats a gigabyte as 2³⁰ bytes, while bitrate and storage use 10⁹. The same recording is therefore both 0.6096 GB and 581.36 MiB.
Does audio need counting separately?
It is already counted: the bitrates are summed before the conversion to bytes. Over an hour, a 128 kbit/s track adds almost 58 MB.
Does this work for variable bitrate?
Approximately. For VBR enter the average bitrate the encoder reports — the result will be close, though not exact to the byte.
What about container overhead?
MP4/MKV metadata, indexes, subtitles and extra tracks depend on the container and file. There is no universal overhead percentage here. The formula estimates only the supplied streams.
How do I pick a bitrate for a target size?
Halving only the video rate while audio stays fixed does not halve the whole file: (4+0.128)/(8+0.128)≈0.50787. Halving duration or the total bitrate halves the modelled size.