Below Par 3.0.2 · last reviewed 7 September 2026
The number Below Par shows you is Below Par's own estimate of your handicap index. It is not an official handicap. It is not issued or endorsed by any golf association, and nothing is ever posted to one. Below Par has no integration with Golf Canada, the USGA, GHIN or any other handicapping authority. If you need an official index — for a club competition, a tournament entry, or anything else where a handicap must be verifiable — obtain it from your national association or your club. Use this one to track whether you are getting better.
The authoritative calculation runs on Below Par's server, from the rounds stored in your account. The app displays that number. The app also carries its own copy of the same arithmetic so it can show you an immediate preview when a round finishes; that preview is never written back, and where it differs from the server's number, the server's number is the one that counts.
This page describes exactly what Below Par does to produce that number. Where the app departs from the 2024 Rules of Handicapping, or approximates something the governing bodies do not publish, it is stated below rather than glossed over.
A handicap index describes how well you play relative to the difficulty of the courses you play on, so that scores from different courses and different tees can be compared. It is built from the best eight of your last twenty scores rather than the average of all of them, which is why it represents your potential rather than your typical round.
Every round that counts produces one score differential:
Score Differential = (113 ÷ Slope Rating) × (Adjusted Gross Score − Course Rating − PCC)
The result is rounded to one decimal place. Positive differentials round normally: 1.55 becomes 1.6. Negative differentials also round normally, except at an exact half, where they round toward zero rather than away from it — so −1.54 and −1.55 both become −1.5, while −1.56 becomes −1.6.
The PCC (Playing Conditions Calculation) term is present in the code and is clamped to the range −1.0 to +3.0, but no part of the app ever supplies a value for it. In every differential Below Par has computed, PCC is zero. A real PCC requires sight of the full field of scores at a course on a given day, which the app does not have, so it does not attempt one.
A round with an Adjusted Gross Score of 95, on a tee rated 71.4 with a Slope Rating of 130:
| Step | Working | Result |
|---|---|---|
| Adjusted Gross Score | as entered, after the per-hole cap | 95 |
| Subtract the Course Rating | 95 − 71.4 | 23.6 |
| Subtract PCC | 23.6 − 0 | 23.6 |
| Slope factor | 113 ÷ 130 | 0.869231 |
| Multiply | 0.869231 × 23.6 | 20.5138 |
| Round to one decimal | 20.5 |
Below Par applies a net double bogey cap. Each hole is capped at par + 2 + the strokes you receive on that hole, and the capped total is what feeds the formula above. The strokes you receive come from your Course Handicap, calculated as Handicap Index × (Slope ÷ 113) + (Course Rating − Par), rounded to the nearest whole number. For a nine-hole round your index is halved first.
That Course Handicap uses whatever index the app is holding at the time. A golfer who has not yet been given an index and did not state one at sign-up is scored against 0.0: the Course Handicap collapses to Course Rating minus par, rounded — zero or below on a tee rated at or under par, one or two strokes on a tee rated above it — so most or all of their holes cap at a flat par + 2 as though they were scratch. Adjusted gross for those first rounds is lower than it should be, the differential with it, and both are stored against the round. This is a defect rather than a design choice, and it is recorded here as one.
The genuine divergence is in how the strokes you receive are spread across the holes. Below Par does not use hole stroke indexes. It divides your Course Handicap evenly across the holes and gives any remainder to the lowest-numbered holes, because the app does not ask you for eighteen stroke indexes and the per-hole data in course feeds has been unreliable. This changes your cap only on holes where you already scored triple bogey or worse. On such a hole, if you would have received a stroke under the official allocation but do not under the even one, the cap is one shot lower and your differential reads slightly lower than an official one; where the reverse happens it reads slightly higher. It does not push consistently in one direction.
Two further specifics. A plus-handicap golfer receives zero strokes rather than giving one back, so their cap is a flat par + 2 on every hole. And a round read back from the server without a stored differential falls through to a cruder cap — par + 2 per hole applied across the whole card rather than hole by hole — which cannot catch a single blow-up hole offset by birdies.
With twenty or more counting rounds, Below Par takes the last twenty, keeps the eight lowest differentials, and averages them. There is no 0.96 multiplier — that was the pre-2020 bonus for excellence, and it is not in this app. The average is rounded to one decimal place.
With fewer than twenty rounds, this table is used. It matches published Table 5.2a exactly, adjustments included.
| Counting scores in your record | Differentials used | Adjustment |
|---|---|---|
| 3 | lowest 1 | −2.0 |
| 4 | lowest 1 | −1.0 |
| 5 | lowest 1 | 0 |
| 6 | lowest 2 | −1.0 |
| 7 to 8 | lowest 2 | 0 |
| 9 to 11 | lowest 3 | 0 |
| 12 to 14 | lowest 4 | 0 |
| 15 to 16 | lowest 5 | 0 |
| 17 to 18 | lowest 6 | 0 |
| 19 | lowest 7 | 0 |
| 20 or more | lowest 8 | 0 |
Below three counting scores there is no index at all, and the app displays N/A. If you entered an estimated index when you signed up, that stated number is shown until three counting rounds exist, at which point the calculated one replaces it.
Once a low handicap index exists for you — the lowest index you have reached — three further adjustments are applied, in this order:
Finally the number is clamped to a maximum of 54.0 and a minimum of −5.0. The 54.0 ceiling is the WHS maximum. The −5.0 floor is Below Par's own limit; the Rules publish no lower bound on a plus handicap.
Every step re-rounds to one decimal place. Nothing is truncated. One inconsistency worth knowing: the exact-half rule described above applies to differentials, but the index itself uses ordinary rounding, so a plus index computing to −1.55 becomes −1.6 while a differential of −1.55 becomes −1.5.
Nine-hole rounds are not doubled, and they are not held aside waiting to be paired with another nine. Each one produces its own eighteen-hole differential immediately, by adding an expected differential for the nine you did not play:
18-hole Score Differential = [(113 ÷ Slope) × (AGS − Course Rating − PCC ÷ 2)] + [(Handicap Index + 3) ÷ 2]
PCC is halved for a nine-hole round, and as everywhere else in the app it is zero. The bracketed nine-hole figure is deliberately left unrounded until the expected component has been added; only the sum is rounded, once.
Worked example, for a golfer at index 14.0 shooting 43 on a nine rated 35.8 with a Slope of 113:
| Step | Working | Result |
|---|---|---|
| Nine-hole differential | (113 ÷ 113) × (43 − 35.8) | 7.2 |
| Expected for the nine not played | (14.0 + 3.0) ÷ 2 | 8.5 |
| Sum, rounded once | 7.2 + 8.5 | 15.7 |
| For comparison, the old doubling method | 7.2 × 2 | 14.4 |
The expected-score formula above is Below Par's own. The Rules describe this calculation as automated and do not publish the model behind it. Below Par reverse-engineered a straight line from the governing bodies' single worked example — the one reproduced in the table, which it matches exactly. The official model is statistical rather than linear, so differences should be expected at the extremes of the handicap range.
The expected component depends on whatever index the app is holding. If you stated one at sign-up, that is what is used. If you did not, the app passes 0.0, so the expected component is (0 + 3) ÷ 2 = 1.5 rather than your real figure, and that differential is stored against the round. This has the same cause as the defect described under Adjusted Gross Score above.
Playing nine holes on a tee rated for eighteen: the Course Rating and par are halved to match the holes played, and the Slope is carried across unchanged, since Slope is a ratio and does not scale. Halving is an approximation — the two nines of a course are rarely equal, and the app does not use the nine's own published rating.
Below Par does not invent a rating and then quietly count the round.
If a tee in the course database has no published Course Rating and Slope, it is not offered in the tee picker at all. A course can therefore appear with a short tee list, or none.
If you play without selecting a tee, or you add a tee by hand and leave the rating and slope blank, the app fills in a placeholder — Course Rating equal to par, Slope 113 — so the round can still be scored and stored. That round is flagged as not counting. It appears in your history, your scoring trends and your statistics, but it is excluded from the handicap index calculation on both the server and the device. The round-complete screen says so: no rating for these tees, so this round does not count toward your index, and adding a rating in the tee sheet will change that.
One consequence to be aware of. When you add a tee by hand without a rating, the tee is remembered against that course as one you entered yourself. The round you are playing is unaffected, but the next round you play at that course will pick that tee up as a rated one and will count toward your index — using the placeholder rating of par and 113. If you add a tee, add its real rating and slope.
Below Par tracks four sources for a tee's rating: the bundled course database, GolfCourseAPI, a rating you entered yourself, and an estimate. The tee picker shows either a rating and slope — "Par 72 · 71.3 / 129" — or "Par 72 · No rating", with "Added by you" on tees you created. The round-setup row shows the same two forms without that note. The full sentence naming the source is shown on the summary card before you submit a scorecard you are transcribing after the fact.
Listed roughly by how much each one can move a real number.
Every differential is computed with a Playing Conditions Calculation of zero. This is defensible — the Rules set PCC to zero when fewer than eight acceptable scores are returned, and the app only ever sees its own users — but it means there is no route by which a published PCC could reach your differentials.
Described in full under Adjusted Gross Score above. It affects the net double bogey cap only on holes where you scored triple bogey or worse, and it can move your differential in either direction.
Rule 5.8 measures the soft and hard caps against your lowest index in the last 365 days. Below Par stores an all-time running minimum instead; nothing applies a date window to it. Your best-ever index therefore caps you permanently. If you played well two years ago and have since got worse, the caps will hold your index down further than an official calculation would.
Rule 5.9 reduces each differential in your record, so the reduction ages out as those scores leave the twenty-round window. Below Par subtracts from the finished index instead, and re-evaluates it on every recalculation. The number today is the same; twenty rounds from now it will not necessarily be.
Described under Nine-hole rounds above.
The rating is halved rather than taken from the nine's own published rating.
The index is floored at −5.0. The Rules publish no such floor.
Nothing about your handicap leaves Below Par. When the app asks the course-data provider for a tee's rating, only the course name is sent. Finding courses near you is a separate step that sends your coordinates to Apple's MapKit, which returns names and locations only — never ratings. When the app generates written insight about your game, it sends aggregate scoring statistics: no index, no differentials, no course rating, no course name.