If you want to compete at all levels of golf, you need a handicap (or handicap index, as it is more appropriately termed). There are a number of organizations that provide the golfer with a handicap, though the primary governing body is the United States Golf Association. The USGA has licensed a system, the GHIN service, to provide a handicap index.
Find course and slope ratings. Member courses with a signed licensing agreement to use the GHIN service will have USGA course and slope ratings for each set of tees. They are usually displayed in the golf shop, locker room or clubhouse. They also are usually on the course scorecard.
Play 20 rounds. You need a minimum of 20 golf scores to best establish an accurate handicap index. A minimum of five scores is allowed, but not preferred. Your scores must be adjusted with the USGA Equitable Stroke Control. These are the established maximum scores a golfer can have on each hole. You can find the tables at www.usga.org.
Convert each adjusted gross score into a handicap differential. Use the following formula: (adjusted gross score - USGA course rating) x 113 / USGA slope rating = handicap differential
Once the handicap differential has been determined for each score, add together 10 recent, low handicap differentials. Divide this number by 10 (number of rounds counted) to find your average. Multiple this average by .96, round to the nearest tenth, and you have your handicap index.