A portable, one-decimal number representing a golfer's demonstrated ability under the World Handicap System, usable at any compatible course worldwide. It's calculated as the average of the best 8 Score Differentials from a golfer's most recent 20 rounds, multiplied by 0.96 (the WHS bonus for excellence). Each Score Differential is itself (Adjusted Gross Score − Course Rating) × (113 ÷ Slope Rating), so it already accounts for how hard the course played that day. Golfers with fewer than 20 scores use a sliding table — as few as 3 rounds can produce a provisional index. Because it updates after nearly every posted round, a hot or cold stretch shows up within days, not months. The Index itself isn't used directly for strokes; it converts to a Course Handicap at whatever course is being played.

A portable, one-decimal number representing a golfer's demonstrated ability under the World Handicap System, usable at any compatible course worldwide. It's calculated as the average of the best 8 Score Differentials from a golfer's most recent 20 rounds, multiplied by 0.96 (the WHS bonus for excellence). Each Score Differential is itself (Adjusted Gross Score − Course Rating) × (113 ÷ Slope Rating), so it already accounts for how hard the course played that day. Golfers with fewer than 20 scores use a sliding table — as few as 3 rounds can produce a provisional index. Because it updates after nearly every posted round, a hot or cold stretch shows up within days, not months. The Index itself isn't used directly for strokes; it converts to a Course Handicap at whatever course is being played.