I tried several times to compress a file that is 6 minutes and 33 seconds long. I changed the settings to 24 FPS and I changed the size to 853 x 480. The file is still too big. I've also tried to export it at a lower resolution using NTSC 720 x 480 16:9 and NTSC 720 X 480 4:3. I have kept the compressor quality slider at Best. I need the file to be no bigger than 250MB This has been a very difficult task. I am converting the file to a quicktime movie. This file is to be uploaded to a website.
Some math is in order to figure out what bit rate you should encode at to hit a size target. If your file needs to be (let's say) 200MB, then using H.264 compression, your total bit rate should be around 1500 kbps. I got that figure from this calculator:
Data rate controls file size for the most part.
Compressor's summary tab will show you the estimated file size per one hour so you'd have to do a little math to find the approximate file size. I generally find Compressor's estimate to be as much as 10-20% smaller than the resultant encode.