Golf Handicap Calculator Formula

Understand the math behind the golf handicap calculator. Each variable explained with a worked example.

Formulas Used

Handicap Index (estimate)

handicap_index = round(avg_diff * 0.96 * 10) / 10

Course Handicap

course_handicap = round(avg_diff * 0.96 * slope_rating / 113)

Best Differential

best_diff = round((diff1 < diff2 ? (diff1 < diff3 ? diff1 : diff3) : (diff2 < diff3 ? diff2 : diff3)) * 10) / 10

Variable	Description	Default
`score1`	Score (Round 1)	92
`score2`	Score (Round 2)	88
`score3`	Score (Round 3)	95
`course_rating`	Course Rating	72
`slope_rating`	Slope Rating	125
`diff1`	Derived value`= (score1 - course_rating) * 113 / slope_rating`	calculated
`diff2`	Derived value`= (score2 - course_rating) * 113 / slope_rating`	calculated
`diff3`	Derived value`= (score3 - course_rating) * 113 / slope_rating`	calculated
`avg_diff`	Derived value`= (diff1 + diff2 + diff3) / 3`	calculated

Score Differential = (Score - Course Rating) x 113 / Slope Rating

Handicap Index = Average of Best Differentials x 0.96

The official USGA system uses the best 8 of 20 most recent differentials. This simplified calculator uses 3 rounds to give an estimate.

Course Rating: The expected score for a scratch (0-handicap) golfer. Typically 68-74.

Slope Rating: Measures difficulty for bogey golfers relative to scratch golfers. Range is 55-155, with 113 being standard.

Calculate handicap from scores of 92, 88, and 95 on a course rated 72/125.

score1 = 92score2 = 88score3 = 95course_rating = 72slope_rating = 125

01Differential 1 = (92 - 72) x 113/125 = 20 x 0.904 = 18.08.
02Differential 2 = (88 - 72) x 113/125 = 16 x 0.904 = 14.46.
03Differential 3 = (95 - 72) x 113/125 = 23 x 0.904 = 20.79.
04Average = (18.08 + 14.46 + 20.79) / 3 = 17.78.
05Handicap Index = 17.78 x 0.96 = 17.1.

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