When I started out, I used this as a guide. http://wiki.polycount.com/wiki/Freelance#Freelance_Rates Id also factor in how strong your work is and if you have experience working in a company.
its pretty strange though , theres no real way to know if you over or undercharge compared to others unless you straight up ask them. and then you`re usually presented with "calculate". I do understand that prices vary from person to person and their cost of living but if you dont have any kind of average to go off by you…