Reduce Video Bitrate

Bitrate and size

Bitrate is how many bits are spent per second of video and audio together. Size in MB is roughly total bitrate in Mbps × seconds ÷ 8. A 4-minute clip at 3 Mbps of video plus 128 kbps of audio comes to about (3 + 0.128) × 240 ÷ 8 ≈ 94 MB.

There is no bitrate field. To hit a bitrate, work out the size and type it: click the After size in the estimate row (pencil icon) and enter the MB. The page aims 1.5% under the number you type to leave room for the container, and subtracts the audio before setting the video bitrate.

The numbers this page starts from

For MP4 (H.264) at 30 fps the opening target works out to about 0.8 Mbps of video at 480p, 1.8 Mbps at 720p, 4 Mbps at 1080p, 7 Mbps at 1440p and 16 Mbps at 2160p. Frames above 30 fps count at half weight, so 60 fps gets 1.5 times these figures.

If the Format is MP4 · HEVC when you pick the video, the opening target is 65% of the H.264 figure; for WebM (VP9) it is 70% and for WebM · AV1 55%. Changing the format afterwards keeps the size you set. The target is never set above the source's own video bitrate. If there is nothing to save, the estimate row says "At this setting the file stays about the same size."

When the bitrate is too low for the resolution

Below about 0.025 bits per pixel per frame (H.264), the picture breaks into blocks. If your target would go under that at the current Screen size, the panel moves down the resolution steps until it doesn't, marks that row with a dashed amber frame and says "Resolution set to W × H to reach this size." If even the lowest step is not enough, it may also say "Audio set to 64 kbps to reach this size."

So resolution is kept only while the target allows a usable bitrate. To keep it, raise the size, or save space elsewhere: set Frame rate to 30 fps, or set Audio to 64 kbps or Remove audio.

Frequently asked questions