Leveling the Fairway
Golf is unique among sports because it allows a complete amateur to play a competitive match directly against Tiger Woods and have a mathematically fair chance of winning. This is achieved through the Handicap System.
A golf handicap is a numerical measure of a golfer's potential ability. It dictates exactly how many "free strokes" you are allowed to subtract from your actual score to level the playing field against a scratch golfer (someone with a handicap of 0).
The Complexity of the Differential
You cannot calculate a true handicap index from just one round of golf. The USGA requires you to track your best 8 rounds out of your last 20. However, the foundation of the entire system requires calculating the Handicap Differential for every single round you play.
The Formula
The differential formula accounts for the fact that shooting an 85 on a flat, easy local course is much less impressive than shooting an 85 on a brutally difficult professional championship course.
Differential = (Gross Score - Course Rating) * 113 / Slope Rating
Rating vs. Slope
- Course Rating: What a scratch golfer (0 handicap) is expected to shoot. (e.g., 71.5 on a par 72 course).
- Slope Rating: A multiplier measuring how much harder the course is for a bogey golfer compared to a scratch golfer. The baseline standard difficulty is 113. A horrific, hazard-filled course might have a slope of 145.