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Golf Handicap Calculator

Computes a golf Handicap Index under the World Handicap System (USGA/R&A) from 3–20 adjusted gross scores: each score differential = (score − course rating) × 113 / slope rating, the index is the average of the lowest differentials selected by the WHS table (with −2.0 / −1.0 adjustments for 3, 4 and 6 scores), and optionally the Course Handicap for a given par.

When to use

You have a golfer's recent 18-hole adjusted gross scores with the course rating and slope rating and need the WHS Handicap Index, the score differentials or the Course Handicap for a set of tees.

Do not use when: You need an official handicap (only a club or association system with playing-conditions and cap adjustments issues one), the scores are from 9-hole rounds, or the rounds were played on tees with different ratings (compute each differential with its own rating first).

Formula

differential_i = round0.1((score_i − course_rating) × 113 / slope_rating); handicap_index = min(54.0, round0.1(mean(lowest n differentials) + adjustment)) with (number of scores → n, adjustment): 3 → 1, −2.0; 4 → 1, −1.0; 5 → 1, 0; 6 → 2, −1.0; 7–8 → 2, 0; 9–11 → 3; 12–14 → 4; 15–16 → 5; 17–18 → 6; 19 → 7; 20 → 8; course_handicap = round(handicap_index × slope_rating / 113 + course_rating − par)

World Handicap System, Rules of Handicapping Rule 5.2 (score differentials and Handicap Index calculation) and Rule 6.1 (Course Handicap). The playing conditions calculation (PCC), soft and hard caps, exceptional-score reductions and 9-hole score combination are not applied, and all scores are assumed to come from tees with the given rating and slope. Informational, not an official handicap.

Inputs

Parameter	Type	Required	Description
`scores`	number_list	yes	3–20 adjusted gross scores (18 holes, net double bogey applied), most recent last; only the most recent 20 rounds count under WHS.
`course_rating`	number	default 72	USGA/R&A course rating of the tees played (assumed the same for all scores). Range: ≥ 40, ≤ 90
`slope_rating`	integer	default 113	Slope rating of the tees played (55–155; 113 is standard difficulty). Range: ≥ 55, ≤ 155
`par`	integer	no	Par of the tees played; when given, the Course Handicap is also reported. Range: ≥ 54, ≤ 80

Outputs

Output	Type	Description
`handicap_index`	number	Average of the lowest score differentials per the WHS table plus the adjustment, rounded to 0.1 and capped at 54.0; a negative value is a 'plus' handicap (e.g. −2.0 = +2.0).
`differentials`	number_list	(score − course_rating) × 113 / slope_rating for each score, in input order, each rounded to 0.1.
`differentials_used`	integer	How many of the lowest differentials are averaged (1–8, depending on the number of scores).
`adjustment`	number	WHS adjustment added to the average: −2.0 with 3 scores, −1.0 with 4 or 6 scores, otherwise 0.
`course_handicap`	integer	handicap_index × slope_rating / 113 + (course_rating − par), rounded to the nearest whole number (only when par is given).
`method_text`	string	Which WHS table row was applied and which differentials were averaged.

Example

5 scores, CR 72, slope 130, par 72: {"scores":[88,92,85,90,95],"course_rating":72,"slope_rating":130,"par":72} → {"differentials":[13.9,17.4,11.3,15.6,20],"handicap_index":11.3,"differentials_used":1,"adjustment":0,"course_handicap":13}

6 scores, CR 71.5, slope 125, par 72: {"scores":[95,90,88,92,86,91],"course_rating":71.5,"slope_rating":125,"par":72} → {"differentials":[21.2,16.7,14.9,18.5,13.1,17.6],"handicap_index":13,"differentials_used":2,"adjustment":-1,"course_handicap":14}

GET https://tttkmbb.com/api/v1/calculate/golf-handicap?scores=88%2C92%2C85%2C90%2C95&course_rating=72&slope_rating=130&par=72

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/golf-handicap (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/golf-handicap · Markdown: https://tttkmbb.com/fitness/golf-handicap.md · JSON definition: https://tttkmbb.com/fitness/golf-handicap.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="golf-handicap"
OpenAPI operationId: calculate_golf_handicap_index
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Why does this differ from my club's Handicap Index?

Official systems apply a playing conditions calculation (−1 to +3) to each round, cap upward movement and use every round's own course rating and slope; this calculator assumes one rating for all scores and PCC 0.

What is an adjusted gross score?

The gross score after limiting each hole to net double bogey (par + 2 + any handicap strokes received on that hole), the WHS maximum hole score for handicap purposes.

Which Course Handicap formula is used?

The WHS formula Handicap Index × (slope ÷ 113) + (course rating − par), rounded to a whole number. Before the 2024 revision some jurisdictions (e.g. Great Britain and Ireland) omitted the (course rating − par) term.

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