Batch export final size?

Hi, 

I have twenty or somthing video clips and i need to fit them to 20Gb limit. Right now they are much more. Is there a place in media composer where i could see how much space the will it estimately take. Or i just have to take the calculator and manuly figure out that 1hour of 5,5Mbit will thake this much sapce? And i have 20 smth hour os footage 

Thank you.