Burms get anywhere from 10'-18'. Like everything else it depends on the indvidual animal, also females are the ones that get bigger. Burms are not a beginer snake and shouldn't be treated as such. Please do your research before getting one, and remember they can not be moved over state lines.
I am looking into a supposed Dwarf Burm myself atm.
The import lists it as a Dwarf Burmese ( Python molurus bivittatus). I can't find enough info on dwarf bivittatus to comfortably import these.I hope they are actually Dwarf Tiger Pythons(Python molurus progschai) and, am awaiting confirmation before placing an order.
If size is a concern (as it is for me), these might be worth looking into. Progschai are significantly smaller than a Burm, built a bit leaner and with more intense patterns.
If you are in the US, Bob Clarke has or had some. I just couldn't say if these got caught up in the Lacey Act that you have to deal with down there.