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There used to be but not anymore. I usually set the slider to 23 and that gives me a file between two and five gig.
 
There is actually but it involves some math.

Change the settings from Constant Quality to Variable bit rate. If you are doing this, I would strongly recommend you do a 2-pass encode as well, which will double your encoding time, but give you a much better encode. You can also set turbo first pass if you like which has a very small degrade of quality and shortens your first pass by about 50%. If you are looking to have every encode less than 4GB I would say a bit rate around 3500 should get you between 2GB-4GB encodes depending on the length of the movie.
 
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