about LJ unit : perm0

in LJ unit:
charge = reduced LJ charge, where q* = q / (4 pi perm0 sigma epsilon)^1/2

I am using LJ unit in my simulation and now i want to find the corresponding system in reality. I am unclear what the "perm0" equals. Does it have a exact form? For future use, can you please inform me how to find it?

Thank you!