The method
Every heat, against the right bar.
Every CT heat ends with a number. Trim asks a better question of it: was that more or less than a surfer normally posts in that round? Below, every heat Griffin Colapinto surfed in 2024 and 2025 lands against that expectation, and the gap pours into his Trim. The bar is set by the round alone, not by the break or the conditions.
1 · The problem
14.43 and 14.40: one strong, one short.
Colapinto posted 14.43 in the opening round of the Surf City El Salvador Pro 2024 and 14.40 in the final of the VIVO Rio Pro 2025. Almost the same number. The first was a big score for its round; the second was just under what that round normally takes.
14.43
Datum 10.72
+3.71
14.40
Datum 14.49
−0.09
A heat total on its own can't tell you which. Rounds get harder as an event goes on, so the same number means very different things in different places.
2 · Datum
Datum rises from 10.72 to 14.49.
Datum is what a typical CT surfer posts in that round, worked out from every heat of 2024 and 2025. It rises as the field thins and the waves get chosen more carefully.
- Opening Round10.72
- Qualifying Round11.17
- Elimination Round11.47
- Round of 3211.74
- Round of 1612.04
- Quarterfinals13.05
- Semifinals13.75
- Final14.49
The maths
This first version of Datum holds one expected heat total per round, fitted on every heat result of 2024 and 2025 that carries a published total. Venue, wave height and wind are not in the line; they appear instead in each surfer's condition splits.
Every figure above is read from the model's stored output, not typed.
3 · The gap
The gap is posted minus Datum.
Take the posted total and subtract Datum. That gap is the whole idea: yellow when a surfer beat what the round normally produces, blue when he fell short. It's the same measure whether it's a Pipe opening round or a WSL Finals title match.
Across his 85 heats, Colapinto finished above the line in 58 and below it in 27.
Try it · a heat Colapinto might surf next
From 1.470 today. One heat moves Trim 4.5% of the way towards its gap, so a single result nudges it rather than swings it.
4 · Trim
Each heat moves Trim 4.5%.
Trim adds up the gaps, but not equally. Each new heat counts for 4.5%, and everything before it shrinks a little to make room. A heat's weight halves roughly every 15 heats. Every surfer starts at zero, and that starting point fades too: after 85 heats it holds just 2.0% of Colapinto's rating, which is why he can be rated with confidence and a rookie can't yet. His Trim today is 1.470.
The maths
Trim after a heat = 0.0452 × gap + 0.9548 × Trim before, starting from 0.
So a heat surfed k heats ago counts 0.0452 × 0.9548k today, and the starting zero still counts 0.9548n after n heats. That last figure is the "prior weight" shown beside every rating. The rate is the same for every surfer.
5 · Points and Trim
Points record results. Trim summarises scoring against the round.
Ranking points reward where you finish. That's the right way to crown a champion, but it's a noisy way to judge surfing: one hot event lifts a season, a tough draw sinks one, and every heat in between is invisible. Trim reads every heat against the typical score for its round, and weighs the most recent heats most. It is a summary of scoring, not a full measure of surfing ability: later rounds have stronger fields, so some skill is in the bar as well.
Take the 22 rated surfers who surfed every 2025 event and rank them twice: by 2025 points, and by Trim. On the dashed line the two agree. Alan Cleland is 19th on points but 10th on Trim: his heats were better than his results. Jordy Smith is the opposite, 2nd on points and 12th on Trim. Trim covers both seasons, so it also carries 2024 form.
6 · What it unlocks
What Trim makes possible.
- ConditionsOn the siteOn every surfer page: his gap by the wave height and wind WSL published for each heat.
- The whole fieldOn the siteOn the home page: every surfer as a ridgeline, so a run of form shows at a glance.
- Head-to-head recordsOn the siteOn Compare: how two surfers did when they met, and against Datum.
- FormPlannedHis last ten heats against his own average.
- MomentumPlannedWhich way his Trim has moved lately, and how fast.
- Late roundsPlannedDoes he lift from the quarterfinals on, or fade?
- Head-to-head forecastsPlannedA win chance for any two surfers, stored before the heat and scored after it.
7 · What it can't do
What Trim can’t tell you.
- It doesn’t know which way the wave broke. WSL doesn’t publish wave direction for ocean events, so a natural-footer and a goofy-footer at the same break are treated alike.
- It doesn’t model individual judges. It works from heat totals, which already include the judging.
- It doesn’t know who you were up against. Datum is the round’s line, not your opponent’s. Head-to-head forecasts handle the matchup separately.
- Its forecasting edge is small, and not fully tested. On 297 heats from 2025, a head-to-head model built on Trim picked the winner 57.9% of the time, against 50% for a coin flip. With that many heats, the true figure could be anywhere from about 52% to 64%. And it flatters the model, because Datum and Trim were fitted on 2025 as well as 2024. As a predictor of the next heat score, Trim barely beats a plain average. Forecasts aren’t shown on the site yet.
- New surfers need time. With few heats, most of a rating is still the starting zero. That’s why the main tables only rank surfers with 16 or more heats.