Handicaps
How the Handicap Index is calculated
By Caddyio · Updated
Your Handicap Index is the average of the best 8 Score Differentials from your most recent 20 acceptable scores. Each round is first turned into a Score Differential — how well you played relative to the course's difficulty — then the system takes your 20 latest differentials, keeps the lowest 8, averages them and multiplies by 0.96. Until you have 20 scores, a reduced-count table is used, and safeguards cap how fast your index can rise.
1. Turn each round into a Score Differential
Every acceptable score becomes a Score Differential using the course and slope ratings for the tees you played:
Score Differential = (113 / Slope Rating) x (Adjusted Gross Score - Course Rating - PCC)
The Adjusted Gross Score applies a net double bogey maximum on each hole, and the PCC is a daily playing-conditions adjustment that is usually zero.
2. Keep the best 8 of your last 20
The system looks at your 20 most recent differentials, sorts them, and keeps the lowest 8. Those are the rounds where you played closest to your potential — which is why the Index reflects demonstrated ability, not your average.
3. Average and scale
Average those 8 differentials and multiply by 0.96. The result, rounded to one decimal, is your Handicap Index.
4. Fewer than 20 scores
With fewer than 20 rounds, a sliding table decides how many count — for example the best 1 of your first 3 scores, or the best 3 of 6-8 — often with an adjustment while your record is thin.
5. Built-in safeguards
Two limits protect your Index from a run of bad rounds: a soft cap slows increases beyond 3.0 above your Low Handicap Index, and a hard cap stops it rising more than 5.0. A good day still moves it straight away.
Frequently asked
- Is it really only the best 8 rounds that count?
- Yes. From your most recent 20 acceptable scores, only the lowest 8 Score Differentials are averaged, then multiplied by 0.96.
- How many scores do I need for a Handicap Index?
- You can get an initial Index after a single 18-hole score (or two 9-hole scores), but it becomes far more reliable once you have 20 rounds on record.
- Does Caddyio give me an official handicap?
- No. Caddyio shows an indicative Handicap Index for engagement and lets you export scores to your club's handicap secretary. Your official record stays with your union-connected provider.
Caddyio tracks an indicative Handicap Index from members' rounds — best 8 of 20, with trends — and exports scores for your handicap secretary. It is an engagement tool, not the official WHS record.