How to calculate a golf handicap, step by step
To calculate your golf handicap: (1) take your adjusted gross score for each round, (2) turn each round into a score differential using (113 ÷ Slope) × (Score − Course Rating), (3) keep your lowest 8 differentials from your last 20 rounds, and (4) average them. The result, rounded to one decimal, is your Handicap Index.
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Step 1 — Adjust your gross score
Before any math, each hole score is capped at net double bogey (par + 2 + any handicap strokes you receive on that hole). This stops one blow-up hole from wrecking the calculation. If you took a 9 on a par 4 where you get one stroke, it counts as 7 (4 + 2 + 1). Sum the capped holes — that is your adjusted gross score.
Step 2 — Compute each round's score differential
Score Differential = (113 ÷ Slope) × (Adjusted Score − Course Rating)
Course rating and slope are printed on the scorecard for the tees you played. Example: you shoot an adjusted 88 from tees rated 71.2 with a slope of 128:
(113 ÷ 128) × (88 − 71.2) = 0.883 × 16.8 = 14.8
Compute one differential per round. You can check any single round with our score differential calculator.
Step 3 — Keep your lowest 8 of the last 20
List your differentials from your most recent 20 rounds and keep the lowest 8. With fewer than 20 rounds, WHS uses a reduced table — from 3 rounds (lowest 1, minus 2.0 adjustment) up to 20 (lowest 8, no adjustment). You can establish a first index with just 54 posted holes.
Step 4 — Average and round
Average the kept differentials and round to one decimal. Say your best 8 are 12.8, 13.4, 14.1, 14.8, 15.0, 15.5, 16.2, 16.9 — the average is 14.8, so your Handicap Index is 14.8. To know your strokes at a specific course, convert it with the course handicap calculator.
Skip the spreadsheet
This is entirely mechanical — which is exactly why software should do it. Our free golf handicap calculator runs the full WHS math in your browser, and the Flash Caddie app recalculates your index automatically every time you finish a round.
Frequently asked questions
- How many rounds do I need to calculate a handicap?
- A minimum of 54 holes — three 18-hole rounds or six 9-hole rounds. The index stabilizes as you approach 20 rounds, when the full best-8-of-20 calculation applies.
- What if my course has no rating or slope?
- Rounds on unrated courses cannot produce a valid differential and are excluded from handicap calculation. Most rated courses print rating and slope on the scorecard for each tee.
- Can I calculate a handicap from 9-hole rounds?
- Yes. Under current WHS rules a 9-hole score is converted to an 18-hole differential (your 9-hole differential plus an expected differential for the unplayed nine), so 9-hole golf counts fully.
- Is the calculation different for GHIN?
- No — GHIN is the USGA’s posting service and uses exactly this WHS math. Calculating it yourself (or in an app) gives the same number; GHIN membership is what makes it official for competitions.
Keep reading
Your index, computed after every round
Score your round hole-by-hole in Flash Caddie and your WHS Handicap Index updates itself — differentials, best-8 selection, and reduced tables handled for you. Free on iOS.