Video file size calculator

What the calculator does

You give it a video bitrate, an audio bitrate and a duration. It returns the estimated file size in decimal units (MB, GB) and in binary units (MiB, GiB), because tools and platforms mix the two. A second mode works backwards: give it a target size and a duration, and it returns the video bitrate you can afford once the audio is taken out.

Below the result it lists the upload limits of the platforms we have read official figures for, and marks each one as fits, unclear or does not fit. For every platform it also shows the longest video that would stay under the size limit at your bitrate. The calculator never asks for a file. You type numbers, so nothing is uploaded, and it makes no network calls.

How to use it

1. Pick a preset or type your own video bitrate. The presets are YouTube's recommended SDR upload bitrates; the 1080x1920 preset reuses the 1080p figure, which is our assumption because YouTube's table covers 16:9 only.
2. Set the audio bitrate. 128 kbps and 384 kbps are the two common choices; use No audio for a silent file.
3. Enter the duration in hours, minutes and seconds.
4. Read the estimate, then scroll through the list to see which platform limits it passes.
5. To plan an export for a size cap, switch to Bitrate for a size, enter the cap and the duration, and use the bitrate it gives back.

The bitrate presets and where they come from

YouTube publishes recommended upload bitrates for standard dynamic range video. Standard frame rate means 24, 25 or 30 fps; high frame rate means 48, 50 or 60 fps. These are recommendations, not limits. YouTube's page also says no bitrate limit is required.

For audio, YouTube recommends 128 kbps for mono and 384 kbps for stereo. Meta lists 128 kbps or more for stereo AAC on Reels. The calculator's 4K preset uses the low end of YouTube's range.

The upload limits it checks

Only limits that appear on a platform's own help, ads or developer page are included, each with its link in the Details row of the tool. Where a platform writes MB or GB without saying whether it means 1,000-based or 1,024-based units, the tool treats the limit as a range and reports a file that falls inside it as unclear instead of guessing.

These limits change. If the tool and the platform disagree, the platform wins; open the source link in the Details row and check its date.

Worked examples

The last row shows the use of the second mode: to keep a three-hour file inside 10 GB you need a combined bitrate under roughly 7.9 Mbps, so around 7.8 Mbps of video with 128 kbps audio.

What the number does not tell you

• It is an estimate. Variable-bitrate encodes land near the target, not on it, and the container adds a small amount of its own data.
• A bitrate that suits one resolution is not a quality guarantee for another. The presets are what YouTube recommends for uploads, not a measure of how the picture will look.
• MB and MiB differ by about 5 percent, and the gap grows with the unit: GB and GiB differ by about 7 percent. When a platform page writes only GB, assume the lower figure if you are close.
• Limits are about the file you upload. This tool does not read a file, so it cannot tell you the size of one you already have. Your operating system's file properties show that.
• Safe-zone margins, aspect ratios and caption rules are separate questions. Several platforms publish them for ads only, and some publish no pixel figures at all.

Where KeyMo fits

This calculator tells you whether a source or an export will fit. It does not cut anything. KeyMo is the paid tool that does: upload an MP4 or MOV of 5 minutes to 3 hours, up to 10 GB, and it returns up to 15 scored clips as vertical 9:16, 1080x1920, 30 fps, H.264 and AAC files, with a choice of caption styles or none.

If your recording is close to the upload limit, use the calculator first, then see KeyMo pricing. Related reading: what bitrate means and the LinkedIn video size limits.