Joules in a beta particle

Hello all,

I have been researching radiation and the beta decay of certain elements. I would like to find out how much radiation the human body would absorb (measured in sivs). One siv is 1 joule / kilogram, and so, I need to find out how many joules there are in a beta particle. Is there a way to find it out, or is there a universal constant for the joules in a beta particle? Thank you!