The World Handicap System (WHS) — introduced in 2020 by the R&A and USGA to unify six regional systems — gives every golfer a single, portable Handicap Index that can be converted to a Course Handicap on any rated course worldwide. This calculator applies the full WHS formula so you can track your index from your actual scorecards.
How it works
Step 1 — Score Differential (one round)
Each round produces a Score Differential that normalises your performance to a standard course:
Score Differential = (Adjusted Gross Score − Course Rating) × (113 / Slope Rating)
- Adjusted Gross Score — your total strokes after applying the WHS net-double-bogey hole cap.
- Course Rating — the expected score for a scratch golfer from those tees (e.g. 71.4).
- Slope Rating — how much harder the course plays for a bogey golfer; standard is 113, range 55–155.
The constant 113 keeps the differential on a consistent scale regardless of course difficulty.
Step 2 — Select the best differentials
WHS uses only your lowest (best) differentials, not all of them. The count scales with how many rounds you have submitted:
| Rounds | Best used |
|---|---|
| 3 | 1 |
| 4–5 | 1 |
| 6–8 | 2 |
| 9–11 | 3 |
| 12–14 | 4 |
| 15–16 | 5 |
| 17–18 | 6 |
| 19 | 7 |
| 20 | 8 |
Step 3 — Calculate Handicap Index
Handicap Index = Average of best differentials × 0.96, truncated to 1 decimal place, capped at 54.0.
The 0.96 factor is a built-in softening mechanism to stop an unusually good run producing an unrealistically low index. WHS also applies small negative adjustments (−2.0 for 3 rounds, −1.0 for 4 rounds) to account for the statistical unreliability of a tiny sample.
Worked example
You enter five rounds:
| Round | Adj. Gross | Course Rating | Slope | Differential |
|---|---|---|---|---|
| 1 | 92 | 71.4 | 128 | 18.1 |
| 2 | 89 | 70.8 | 120 | 17.1 |
| 3 | 94 | 72.1 | 130 | 18.8 |
| 4 | 87 | 71.0 | 115 | 15.7 |
| 5 | 91 | 71.9 | 125 | 17.2 |
Five rounds → WHS uses the 1 best differential → 15.7 (from round 4).
Handicap Index = 15.7 × 0.96 = 15.072 → truncated to 15.0
With 6 or more rounds the tool takes more differentials, producing a more stable index.
Formula note
Score differentials can be negative (you scored below the course rating, as a scratch player might). The Handicap Index can be negative too, down to −9.9 under WHS, though the calculator displays it correctly in that case. The 0.96 multiplier and truncation — not rounding — are both required by the official WHS specification.