CHV Letter Grades: A Clearer View of Win Probability

What K, A, B, C, and X mean—and why a horse's grade can change after scratches.

Charting Horse Value letter grades are a quick way to read the model. They are fundamentally another representation of modeled win probability (W%), compressed into five useful groups. The grade helps you scan a field quickly; W% remains the more precise estimate.

The grades track the model's expected win rates

The current CHV results sample contains 69,164 starts and 9,901 wins. Actual win rates by grade closely match the levels around which the model is designed:

• K: 1,309 wins from 2,784 starts — 47.0% actual versus an approximate 46% model level.
• A: 1,817 wins from 5,519 starts — 32.9% actual versus an approximate 32% model level.
• B: 3,384 wins from 17,425 starts — 19.4% actual versus an approximate 20% model level.
• C: 2,279 wins from 22,129 starts — 10.3% actual versus an approximate 10% model level.
• X: 1,112 wins from 21,307 starts — 5.2% actual versus an approximate 5% model level.

That close alignment is the main purpose of the grades. A K horse wins much more often than an X horse because its modeled W% is much higher. The grade does not add a separate opinion on top of W%; it makes that probability easier to see.

These are group averages across many starts, not promises about an individual race. A K horse can lose and an X horse can win. The question in any one race remains whether the probability and the available price create value.

Why grades can change after scratches

CHV grades are dynamic. When a horse scratches, the size and shape of the field change. The model recalculates the remaining horses' win probabilities, and the grade thresholds adjust to the field that will actually run.

That is why a horse may move from one letter grade to another after scratches even though nothing about that horse's past performances changed. The grade is being expressed within a new competitive field.

How minimum upgrades work

Some horses qualify for a minimum grade upgrade based on specific CHV factors or factor combinations. When a qualifying angle is present, the algorithm can establish a higher floor for the horse's grade so the angle is not hidden by the base W% grouping.

An upgrade is a flag to examine the horse more closely. It does not erase the underlying W%, and it does not guarantee a profit. Use the grade with W%, the adjusted morning line (AML), Value, form cycle, and the factors that produced the upgrade.

The X grade is designed to narrow the field

CHV tries to identify approximately 20% of a field as X horses, giving handicappers a practical group of toss candidates. The final percentage will not always equal 20%. If one or more horses qualify for minimum upgrades, fewer horses may remain in the X group.

An X is a strong reason to be skeptical, not a claim that the horse has no chance. In this sample, X horses still won 5.2% of their starts. The objective is to separate low-probability horses from the stronger contenders so wager construction becomes more disciplined.

Win probability is not ROI

Letter grades represent win probability, not return on investment. ROI depends on the price paid. A high-probability K horse can be a poor bet when the odds are too short, while a lower-probability horse can be usable when the price compensates for the risk.

That said, the historical ROI on X horses—and even C horses—is substantially worse than the ROI on K and A horses. That result supports using the lower grades cautiously, but it does not turn the grade itself into a betting instruction. Check AML and Value before deciding whether to bet, pass, single, or spread.

What the + and t suffixes mean

CHV currently uses two letter-grade suffixes:

• + is driven by high Fitness Workout Rating (FWR) in the situations where that factor is most relevant.
• t applies to qualifying horses in turf routes.

Both suffixes identify angles that have produced profitable historical ROI in CHV research. The algorithms can change as the analysis develops. A more detailed review of the two suffixes will be reserved for a future article.

Put the grade in context

Start with the grade for a fast view of the field, then use W% for precision. Check AML and Value to decide whether the price is fair. Review the factor ranks and form-cycle notes to understand why the model sees the horse that way.

The best use of a grade is as a disciplined starting point: identify the strongest win-probability groups, question the tosses, and let price determine whether an opinion becomes a wager.

Next step: Review the CHV Glossary for grade and suffix definitions, watch the CHV tutorials, and apply the model to today's races in the CHV app.