How a handicap index is built
A handicap exists so golfers of different abilities can compete fairly. It is built from score differentials rather than raw scores, because a 90 on a hard course is a better performance than a 90 on an easy one.
For each round the differential is (score − course rating) × 113 ÷ slope rating, where 113 is the standard slope of an average-difficulty course. The lowest differentials are averaged and multiplied by 0.96 to produce the index.
Course rating and slope
The two course numbers do different jobs, and you need both for each round entered.
- Course rating is the score a scratch (zero-handicap) golfer is expected to shoot.
- Slope rating, from 55 to 155, measures how much harder the course plays for a bogey golfer than for a scratch one.
- A higher slope means each stroke over the rating counts for slightly less in the differential.
- Both numbers are printed on the scorecard for each set of tees.
How many rounds count
The official systems use up to your 20 most recent rounds and average only the best 8. This simplified version follows the same idea on a smaller scale: with five or more rounds it averages about the best half, and with fewer it uses only your single best round.
The bar chart shows each round’s differential so you can see which performances are pulling your index down.
A note on accuracy
This is an estimate for casual use, not an official handicap. Sanctioned handicaps apply extra adjustments such as exceptional-score reductions and playing-conditions corrections. For a recognised index, post your scores through an authorised golf association.
Formula
differential = (score − courseRating) × 113 / slopeRating; index = average(best differentials) × 0.96Frequently asked questions
- Why is this an estimate?
- Official handicap systems use up to 20 of your most recent rounds and apply extra adjustments. This simplified version follows the same idea with up to five rounds, so treat it as a guide.