FitCD is a tool to help you calculating the exact image size of a SVCD (authored with vcdimager, Nero or I-Author) or a DVDR.

It includes a resizing calculator for optimal (macro)block-usage in MPEGs. You can also export a sample script for use with AVISynth.

Although at first sight the program seems to offer too much information in too small space, it's actually quite handy once you take a minute to figure it out.