mpg -> xvid gets too big

[Kamagurka]

sooo i have this mpg lying around on my HD that is ~400mb. since that is too large i figured i'd compress it. so i ran it through MiniCalc, entered all the tidbits and minicalc spake "thy output file shall have 185 mb".
in good faith i loaded my mpg file into virtualdub, hit fast recompress, selected xVid and entered the stuff minicalc told me to enter (the bitrate, namely). well, end of story is the output file had a whopping 620 mb.
perhaps i made a mistake in MiniCalc, since i don't undertand the "overhead" bit and just left it as it was...

[Enchanter]

What audio format are you using for the audio of the XviD file?

[Kamagurka]

since i hit directs stream copy on audio, the same one as in the input file...
mp3, i suppose

[Kamagurka]

ok, you solved my problem over at the divx forum; thx.

[Enchanter]

You're welcome.