Change a video's bitrate, or hit a target size in MB

How to use the video bitrate changer

1. Drop a video onto the box or click to choose one.
2. Under Set, choose A bitrate or A target file size.
3. Enter the Video bitrate in kbps (default 2,500, minimum 50), or the Target size in MB (default 25).
4. Choose the Audio bitrate: 64, 96, 128 (default) or 192 kbps.
5. Pick an Output format and press Re-encode. The results show the Predicted size next to the real output size.

What it does and when to use it

Bitrate is how much data each second of video uses. It sets both quality and file size: double the bitrate and the file roughly doubles. This tool gives you the number directly, which is useful when a platform publishes a recommended bitrate, when a broadcast or kiosk player needs a steady data rate, or when an email, chat app or upload form has a strict limit in megabytes.

If you just want a smaller file without thinking about kbps, the video compressor offers quality levels as well. To change the frame rate at the same time, see the video frame rate changer, and to read a file’s current bitrate first, open it in the video info viewer.

How it works

In target-size mode, the video bitrate is:

video bitrate = target size in bytes × 8 × 0.98 ÷ duration in seconds − audio bitrate

The 0.98 leaves 2% for the container. The predicted size uses the same idea backwards:

predicted size = (video bitrate + audio bitrate) × duration ÷ 8 ÷ 0.98

The video is then decoded and encoded again in constant-bitrate mode with your browser’s WebCodecs encoder, and the audio is re-encoded at the bitrate you chose. Mediabunny handles reading and writing in a background worker. Nothing is uploaded.

Worked examples

These figures come from the tool’s own bitrate and size functions.

• Bitrate mode: 2,500 kbps video + 128 kbps audio on a 2-minute clip gives a predicted size of 38.4 MB.
• A 25 MB limit, 3-minute clip, 128 kbps audio: the tool sets the video to about 1,014 kbps.
• The same 25 MB, 2-minute clip: about 1,585 kbps, since the bytes are shared over fewer seconds.
• A 10 MB limit, 60-second clip, 96 kbps audio: about 1,274 kbps.

Limits and tips

• Raising the bitrate does not add quality that was lost earlier. It only makes a bigger file.
• Long clips take time because every frame is encoded again, and the output is held in memory until you download it.
• AVI, WMV and FLV are not read by this tool; convert them first with the video converter.