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Free video file size calculator

This video file size calculator estimates a video's size from duration and video plus audio bitrate, or works backward from a target size to an available video bitrate.

Compare decimal MB and binary MiB, include audio, and choose an optional reserve for the target-size budget. No files are uploaded; this is planning math, not an encoder.

Use the video file size calculator

Results update as you type. All calculations run in your browser; no files are uploaded.

What would you like to calculate?

Example presets (not export recommendations)

Use the finished video duration. Range: 0.001 seconds to 366 days.

Use the video stream rate only; audio is added separately.

Enter 0 for no audio, or sum the rates of all included audio streams.

Estimated media payload

60.96 MB

Binary size
58.136 MiB
Combined video + audio
8.128 Mbps

Container overhead is not included. Actual file size can differ with the encoder, variable bitrate, and additional streams or metadata.

How the video file size calculator works

Bitrate describes bits used per second of media, as explained in MDN's bitrate documentation. Enter average video and audio stream rates, rather than counting audio twice in a combined rate.

  1. For a size estimate, enter the finished duration and the average video bitrate. Choose Mbps or kbps for each stream.
  2. Add the total audio bitrate, or enter zero for a silent export. The result shows media payload in MB and MiB.
  3. For a target-size budget, enter decimal MB and duration. The tool reserves 5% by default, subtracts audio, and allocates the remainder to video. Change the reserve or set it to zero.
  4. Copy the summary, choose export settings in your editor, then inspect the actual exported file.

Payload MB = seconds × (video Mbps + audio kbps ÷ 1,000) ÷ 8

Video Mbps = target MB × (1 − reserve % ÷ 100) × 8 ÷ seconds − audio kbps ÷ 1,000

For example, 60 seconds at 8 Mbps video and 128 kbps audio gives 60.96 MB, or approximately 58.136 MiB, before container overhead. One byte is eight bits; this tool defines MB as 1,000,000 bytes and MiB as 1,048,576 bytes.

Why the exported size can differ

A media container can hold multiple streams and metadata, as MDN's container guide describes. This calculation covers the entered video and audio payload only. Container data, additional tracks, and an encoder's actual average bitrate can change the final size. The reserve is a user-selected margin, not a prediction of those costs.

A resolution label alone is not enough to calculate compressed size. Use a known or planned average bitrate. This tool does not recommend a quality setting, guarantee upload acceptance, or measure a real file. For an existing recording, check its video metadata and the exported byte count.

Common questions

Does this upload or compress a video?

No. You enter numbers and the calculation runs in your browser. It does not read, upload, convert, or compress media files.

Why show both MB and MiB?

This calculator uses decimal MB (1,000,000 bytes) and binary MiB (1,048,576 bytes). They describe the same estimated byte count in different units. Mbps and kbps are decimal bits per second, not bytes per second.

Is a 5% reserve an exact overhead allowance?

No. The default 5% is an optional conservative planning cushion, taken out of the target size before audio is subtracted. It is not a measured overhead percentage and cannot guarantee a file-size limit. Set it to zero to disable it and verify the finished export.

What if the target is too small?

If the audio and reserve consume the target budget, the calculator shows an error instead of a negative video bitrate. Increase the target size or reduce the duration, audio bitrate, or reserve. A positive bitrate alone does not guarantee acceptable picture quality.

Plan and edit your recording

If your material is a real talking-head recording, BlitzCut can help edit supplied UGC, founder-led videos, lessons, and testimonials with transcript editing, adjustable silence removal, captions, and a timeline with images and audio. Measure the finished export when file size matters.