Working out your Handicap Index yourself: the four formulas

Your Handicap Index is calculated overnight, and most people only ever see the result. Work through the four formulas behind it once by hand and three things stop being mysterious: why a result from the harder tees is worth more, why a bad round often changes nothing at all, and why the index sometimes drops by more than a stroke after a good one.

Formula 1: the Score Differential

Every handicap-relevant round is converted back to a course of average difficulty, that is Slope 113. In stroke play the formula reads (Swiss Golf, WHS booklet):

Score Differential = 113 : Slope Rating × (Adjusted Gross Score − Course Rating − PCC)

In Stableford it looks different but means the same: 113 : Slope × (Par + Course Handicap − (points scored − 36) − Course Rating). PCC is the Playing Conditions Calculation, computed overnight from all scores returned that day on that course, and usually zero.

One score, three numbers

Swiss Golf works the same example through for three sets of tees: 90 strokes, once from blue, once from yellow, once from white (WHS in six steps).

Tees	Course Rating	Slope	Par	Score	Score Differential
Blue	69.6	132	72	90	17.5
Yellow	71.9	135	72	90	15.2
White	73.9	137	72	90	13.3

Blue: 113 : 132 × (90 − 69.6) = 17.5. White: 113 : 137 × (90 − 73.9) = 13.3. Four tenths of a handicap more for the same score, purely because the tee is further back. That is the whole idea of the system: making results from courses of different difficulty comparable.

Formula 2: the Course Handicap

Before the round the calculation runs the other way. Your index becomes the strokes you receive on this course from these tees:

Course Handicap = Handicap Index × Slope Rating : 113 + (Course Rating − Par)

Index 15 gives 15 strokes from blue, 18 from yellow and 20 from white. Your target for playing to your handicap is par plus course handicap: 87, 90 or 92. Under the old EGA system the target was the same for everyone, 36 Stableford points. Today each player has their own.

Formula 3: the best eight of twenty

Your index is the average of the eight lowest of your last twenty Score Differentials. Not all twenty. That explains why a bad round frequently does nothing: it lands on your record but not among the best eight, where it only pushes out the oldest result.

The index therefore tracks potential rather than average. Play twenty rounds between 20 and 30 and one at 14, and you will see that one for eight rounds.

When you have fewer than twenty scores

At the start a table of its own applies. It uses fewer results and subtracts something on the first four, so that a first index comes out low rather than high (Swiss Golf):

Scores on your record	What is used	Adjustment
1	the one differential	−2.0
2 or 3	the lowest	−2.0
4	the lowest	−1.0
5	the lowest	0
6	average of the lowest 2	−1.0
7 or 8	average of the lowest 2	0
9 to 11	average of the lowest 3	0
12 to 14	average of the lowest 4	0
15 or 16	average of the lowest 5	0
17 or 18	average of the lowest 6	0
19	average of the lowest 7	0
20	average of the lowest 8	0

A single result is therefore already enough for an index, with two strokes taken off. Pass your course permit, hand in one round, and you are no longer on 54 but on what you played.

Formula 4: soft cap and hard cap

Upwards the index is capped, measured against the Low Handicap Index, the lowest point of the last twelve months. The soft cap halves any increase beyond 3.0 above it. The hard cap stops at 5.0 above the low index. Both only apply once there are twenty scores on your record.

The other direction has the exceptional score: if a differential is at least 7.0 better than the index you played off, every entry so far is corrected down by one stroke, and by two from a gap of 10.0. That is the reason for the occasional jump after a very good round.

Net double bogey caps the single hole

What enters the calculation is not the raw score but the Adjusted Gross Score. The maximum per hole is a net double bogey: par plus two strokes plus the handicap strokes you receive on that hole. A 10 on a par 4 where you get one stroke therefore counts as 7.

That is good for beginners and the reason one disaster does not ruin a handicap. It is also the reason to finish the round rather than give up: a hole you do not hole out still counts, but only at your expected score.

The Playing Conditions Calculation

The formula contains a PCC, and most of the time it is zero. It checks overnight whether the scores returned that day on that course match what was expected, and adjusts them by plus 1 to minus 3 when the deviation is significant (Swiss Golf).

In practice that means a round in wind and rain does not count fully against you if everybody else played worse that day too. It also means you do not know your index in the evening: the final calculation runs overnight.

Playing Handicap against Course Handicap

Two similar terms with one clear difference. Your Course Handicap is the strokes you receive on this course from these tees. Your Playing Handicap is the Course Handicap minus the allowance set in the terms of the competition, for example 90 per cent in four-ball (Swiss Golf).

For General Play and EDS cards the two are identical, because no allowance applies. So playing a card on your own you use the full Course Handicap, and only in a tournament does a percentage appear in the conditions.

Checking the arithmetic is worth doing exactly once

After that the software does it. But looking at the formula changes how you choose your tees and when you hand in a card. From the tees further back the same result is worth more. And a good round only becomes an entry if it was registered as a tournament or as General Play (Swiss Golf).

If you have no index yet, the way there is in From 54 to 36; how nine holes are scored is in Does a 9-hole round count. And what the numbers from a bay have to do with it is in Simulator score against course score.

Frequently asked questions

How do I calculate my handicap myself?

Work out the Score Differential for each round: 113 divided by the Slope Rating, times the difference between Adjusted Gross Score and Course Rating. Your index is the average of the eight lowest of your last twenty differentials.

Why does my handicap not change after a bad round?

Because only the best eight of the last twenty results count. A bad round goes on your record but not into the best eight. It only has an effect once it pushes a good old result out of the last-twenty window.

What is the Course Handicap?

The strokes you receive on a given course from given tees: Handicap Index times Slope Rating divided by 113, plus the difference between Course Rating and Par. Your target for the round is par plus course handicap.

How many rounds do I need for a Handicap Index?

One. With a single result the index is that differential minus 2.0; with two or three it is the lowest minus 2.0. The full rule, the average of the best eight, only applies from twenty results.

What are the soft cap and hard cap?

Brakes against a fast rise. The soft cap halves any increase beyond 3.0 above your lowest index of the last twelve months; the hard cap stops at 5.0 above it. Both apply only from twenty results on your record.

Sources

• Swiss Golf: WHS-Broschüre, Formeln und Glossar (PDF)
• Swiss Golf: WHS in 6 Schritten (PDF) (Rechenbeispiel Blau, Gelb, Weiss)
• Swiss Golf: HCP-wirksame Ergebnisse und General Play