The table further down lists how many differentials count when you have fewer than 20 rounds.
How the handicap calculator works
HandicapCalc follows the World Handicap System. Each round's score differential is 113 divided by the slope rating, times the adjusted gross score minus the course rating minus the playing conditions calculation (PCC), rounded to the nearest tenth. Only your most recent 20 rounds are kept; the lowest differentials among them are averaged according to the table below, the adjustment is added, and the result is rounded to the nearest tenth with a maximum of 54.0. For a course handicap, the index is multiplied by the slope rating over 113 and the course rating minus par is added, then rounded to a whole number; the playing handicap applies the allowance for your format.
Differentials used by number of rounds
| Rounds | Lowest differentials used | Adjustment |
|---|---|---|
| 3 | Lowest 1 | -2.0 |
| 4 | Lowest 1 | -1.0 |
| 5 | Lowest 1 | 0 |
| 6 | Average of lowest 2 | -1.0 |
| 7–8 | Average of lowest 2 | 0 |
| 9–11 | Average of lowest 3 | 0 |
| 12–14 | Average of lowest 4 | 0 |
| 15–16 | Average of lowest 5 | 0 |
| 17–18 | Average of lowest 6 | 0 |
| 19 | Average of lowest 7 | 0 |
| 20 | Average of lowest 8 | 0 |
Example
A 92 on tees with a course rating of 71.3 and a slope of 128 is (113 ÷ 128) × (92 − 71.3) = 18.3. With 8 rounds, the lowest 2 differentials are averaged. A 15.3 index on those tees with a par of 72 is a course handicap of 15.3 × 128 ÷ 113 − 0.7 = 16.6, rounded to 17.
This is an unofficial estimate. Your official Handicap Index comes from your club or national association, which also applies net double bogey limits, soft and hard caps and exceptional score reductions.
Frequently asked questions
When did the World Handicap System start?
It replaced the national systems in 2020, and the rules were updated in 2024.
How often is a Handicap Index updated?
Officially, daily: the day after you post a score.
Do 9-hole rounds count?
Yes. Official systems combine them or calculate an 18-hole differential using an expected score; this calculator takes 18-hole rounds only.
Is HandicapCalc free?
Yes, with no sign-up or ads.
Are my scores saved?
Yes, in this browser only. Nothing is uploaded.