Is there a way to change how the estimate file size is displayed?
For example, my render is set to Windows Media Video, and the estimated file size says '248.05kb/s'. My comp is 17 seconds long so by using my calculator I can estimate that it'll be around 4216kb, or 42mb, but can't I just have it say "Estimated file size: 42mb" rather than telling me how my kb/s it will be? I don't want to have to calcuate it every time I render.
Not that I know and it would fluctuate considerably, anyway. It's just not particularly sensible to predict an absolute file size from a technical POV. Even Size on disk and file size are different and that discrepancy gets biger the bigger the file is. That and of course without analysing the file there's no way to tell predict its size after the compression even halfway reasonably.
There's no need to set the estimated file size. Set your data rate and take what you get.