Reduce video file size without guessing

Start with a size budget and a short test export. Resolution alone is not a file-size setting.

A 100 MB example

For a 5-minute clip with a 100 MB target, the total average bitrate budget is 100 × 8 ÷ 300 = 2.667 Mbps, before container overhead. Reserve 0.128 Mbps for audio and the video budget is about 2.539 Mbps. Actual variable-bitrate output may differ.

Calculate a target bitrate with an overhead allowance.

Change one thing at a time

1. Keep a copy of the original file.
2. Choose the target player and a supported codec.
3. Test a busy 20-second section with motion, fine text and sound.
4. Lower the bitrate gradually; compare at the intended viewing size.
5. Check audio sync, subtitles, file size and playback before exporting the full clip.

What compression cannot fix

A higher output resolution cannot recover detail missing from the original. Repeated lossy exports can accumulate artifacts. For a file that already meets your needs, keeping the original may be the better choice.