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Free online tool

Fit a video under a size limit

Tell it how long the video is and where it is going. You get the bitrate to aim for, a warning if the picture will suffer, and a ready ffmpeg command. Nothing is uploaded; it is just arithmetic in your browser.

About your video

Fit under a size limit

Result

Video bitrate to aim for: 3158 kbps

At this bitrate the picture will look soft at full size.

Lower the picture to 720p (1280×720) to keep it sharp. The command below does that.

ffmpeg command (two passes)

ffmpeg -y -i in.mp4 -vf scale=-2:720 -c:v libx264 -b:v 3158k -pass 1 -an -f null /dev/null
ffmpeg -i in.mp4 -vf scale=-2:720 -c:v libx264 -b:v 3158k -pass 2 -c:a aac -b:a 96k out.mp4

On Windows, replace /dev/null with NUL.

Step-by-step guide for this destination →

Will re-encoding shrink my file?

Enter the size to see how compact the file already is.

Rules of thumb, not promises: how a video looks depends on its content. Check the result by eye.

Why bitrate, not CRF

  • •CRF sets a quality target, not a size. The same CRF gives a small file for one video and a large one for another, so no calculator can turn a CRF into megabytes without your footage.
  • •A size limit is different: file size is bitrate times duration, so the bitrate that fits is exact. Two-pass encoding then aims at that bitrate.
  • •If the bitrate is too low for the picture size, lowering the resolution looks better than keeping a blocky full-size picture. The tool suggests the largest size that still holds up.
  • •A file that is already compact can grow when re-encoded with a low CRF. The last box checks your file and gives a command that cannot make it bigger.

Questions

Is the result exact?
The bitrate is exact arithmetic with about 3% kept free for the container. How good the video looks at that bitrate depends on its content, so the quality hint is a rule of thumb.
Why does the calculator not ask for CRF?
Because CRF does not decide file size. See the guide on why a video gets bigger after compression for measured numbers.
Does it upload my video?
No. You only type numbers; the video never goes anywhere. Run the command on your own computer with ffmpeg.
I do not want to use the command line.
QuickVid Compress on Mac does the same with target-size presets and no commands.

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