Video file size calculator

1. 1

   Pick what to work out

   File size from bitrate, or the bitrate that fits a file size.

2. 2

   Enter the length and bitrates

   Type them in, or tap one of YouTube's recommended video bitrates.

3. 3

   Read the result

   It updates as you type. Use the bitrate in your export settings, or check the size against your limit.

File size is bitrate times length. Bitrates count bits a second, so divide by 8 for bytes: 8 Mbps of video is 1,000,000 bytes a second, about 57 MB a minute. The audio bitrate adds to it.

Most video is encoded at a variable bitrate, so the real file can come out somewhat smaller or larger than the average you set, and the container adds a small overhead.

Work backwards: the size limit, less the audio, spread over the length, is the video bitrate that fits. Export a little under it to leave room for the overhead and the variation.

If the audio alone fills the limit, the video is too long for that size at that audio bitrate. Lower the audio bitrate or split the video.

Add the video and audio bitrates, multiply by the length in seconds and divide by 8. The calculator does it as you type.

At YouTube's recommended 8 Mbps for 1080p at up to 30 fps, plus 128 kbps audio, about 58 MB.

It depends on the length. For a two-minute video with 128 kbps audio it's about 6.9 Mbps of video. Switch to “Bitrate from file size” and enter your own length.

Encoders vary the bitrate from scene to scene, and the container adds a little. The calculation gives the size at the average bitrate.

1,048,576 bytes, as Windows counts. macOS counts 1,000,000 bytes, so it shows the same file as slightly larger.