Change file size based on a standard metric

What I do now is base file size on length of the video. To arrive at this I use a standard, set value, such as 8.33. The typical size of a 21 minute program is 175MB, and the typical size of a 42 minute program is 350MB. These are based on a factor of 8.333... (I hold the 3 until the Windows calculator stops counting them). My theory is that if these programs are acceptable at these sizes, then that same factor can and should apply to all videos I own. Therefore, a 104 minute movie should be 866.6MB (104 X 8.333...). If I have a large batch of files, it requires easy but tedious calculation and entering the number in the "Quality/Size" field for each file. Would would be great would be a metric that you can automatically multiply the files by based on the length of the file. This of course would mean that Movavi Converter recognizes the file length. It would make cataloging files for those who like uniformity or for whom storage is an issue.