How do I calculate my golf handicap? I only play occasionally and usually never do better than 110. Help!?

I am only a casual golfer. People ask me what my handicap is and I don't know how to answer them. What would my approximate handicap be if I normally shoot scores of about 110 or so? I feel ignorant that I can't give an answer and don't even know how a golf handicap is calculated for someone like myself. Please help.