Dosage Index and the Derby

In 1981, the general public — read, horseplayers — became familiar with something that is known as the Dosage Index, a mathematical formula designed to predict a horse's likelihood to be able to successfully negotiate distances of a mile and a quarter, the distance of the Kentucky Derby, and longer.

Daily Racing Form columnist Leon Rasmussen spilled the proverbial beans in the run-up to that year's Derby, based on the findings of Dr. Steven Roman, who identified 120 "chefs-de-race" — sires with exceptional influence on the breed (112 more of these have been added to the list since as of 2019). These sires are placed in one or two of five "aptitudinal groups" — placing these sires on a continuum, in order of the distance preferences of their descendants, from shortest to longest: Brilliant, Intermediate, Classic, Solid, and Professional (in no case can any sire placed in two groups be in groups that are more than two apart in the scheme: Brilliant-Classic, Intermediate-Solid, and Classic-Professional are allowed, but not Brilliant-Solid, Intermediate-Professional, or Brilliant-Professional).

To calculate the Dosage Index, if a horse's sire is a chef-de-race, it counts as 16 points in the applicable group (or if the sire is in two groups, eight points each for both groups). A grandsire counts as 8 points (or if a grandsire is in two groups, 4 points in each group are awarded), a great-grandsire, 4 points (or two in each group if a great-grandsire is in two groups), and for a great-great-grandsire, 2 points (or 1 point apiece if the stallion is in two groups).

The sum of the number of points in the Brilliant and Intermediate groups, plus half the number of the points in the Classic group, is divided by the sum of the other half of the points in the Classic group, plus the number of points in the Solid and Professional groups. The result is the Dosage Index, generally expressed as a figure having two places to the right of the decimal point.

For example, Japanese-bred Crown Pride, who won the 1 3/16-mile United Arab Emirates Derby at the triangle-shaped Meydan Race Course (the former Nad al Sheba Race Course, which Meydan replaced and also in the UAE, was similarly shaped) on March 26, has a Dosage Profile of 5-0-7-2-0, yielding a Dosage Index of 1.55.

That race's runner-up, Summer is Tomorrow, like Crown Pride expected to be in the starting gate at Churchill Downs on May 7, has a Dosage Profile of 3-4-5-2-0, for a Dosage Index of 2.11.

Earlier on the same day, Epicenter won the 1 3/16-mile Louisiana Derby (this race and the UAE Derby are the longest prep races for the Kentucky Derby) in a time of 1 minute, 54 and 1/5 seconds, a new track record for that distance at the 184-year-old racecourse. Epicenter has a stamina-oriented Dosage Index of 0.60, due to his Dosage Profile of 0-0-9-1-2 (horses with no representation in either the Brilliant or Intermediate groups are very rarely encountered, at least on this side of the Atlantic anyway).

Still another probable Derby starter, Tiz the Bomb, who won the Jeff Ruby Steaks — not a misspelling: Jeff Ruby, who is presumably no relation to Jack Ruby, owns seven upscale restaurants in southern Ohio, Kentucky, and Tennessee, five of them steakhouses and the other two seafood-themed, and his chief claim to fame is when he turned away O.J. Simpson, who was in Louisville for the 2007 Kentucky Derby, prompting allegations of racism (the truth is more likely that Ruby is a latter-day Fiorello LaGuardia — a political and ideological eccentric, as Donald Trump is also persona non grata at his establishments), at Turfway Park, formerly Latonia, on April 2, has a Dosage Profile of 3-5-10-2-0, earning him a Dosage Index of 1.86.

To get an idea of what these numbers mean, until Strike the Gold won the 1991 Kentucky Derby with a Dosage Index of 9.00, no horse having a Dosage Index of higher than 4.00 had won the Derby since at least 1929. Since then, however, Strike the Gold's sire, Alydar, was installed as a Classic chef-de-race, retroactively lowering Strike the Gold's Dosage Index to 2.60.

(In addition to the Dosage Index itself, the presence or absence of chef-de-race representation in the Solid and/or Professional aptitudinal groups has, at least historically, been a huge issue in the Derby: From 1940 through 1988, all inclusive, only 1978 Triple Crown winner Affirmed won the Derby without having any Solid or Professional chef-de-race influences; since then, such examples have become more frequent — but only because breeding practices, especially in the United States, have emphasized breeding horses for speed over stamina far more than was formerly the case).

In addition to serving as a useful tool in figuring out which horses to bet on in the Derby, the Dosage Index can also serve as a useful tool in figuring out which horses not to bet on in the Derby — and quite frequently, which horses will not even appear in the Derby field at all.

Hall of Fame trainer D. Wayne Lukas, still going strong at the age of 86, dared harbor Derby aspirations for his filly, Secret Oath — until she weakened to finish third when facing colts in the Arkansas Derby on April 2. Secret Oath, Dosage Index of 8.60 and all, will now be pointed toward the shorter Kentucky Oaks.

Another pedigree-related casualty, so far as Derby contention is concerned, is Forbidden Kingdom: after making the early lead in Saturday's Santa Anita Derby, Forbidden Kingdom stopped colder than yesterday's pizza and finished last. Forbidden Kingdom's ultimate goal is now this autumn's Breeders' Cup Sprint — to which his Dosage Index of 9.00 ideally suits him.

While Epicenter is the likely Derby favorite, Tiz the Bomb figures to be around 20-1, Crown Pride 50-1, and Summer is Tomorrow maybe even 99-1 (tote boards do not accommodate 100-1 or higher).

If that superfecta comes in, regardless of in what order, the return will be "big balloons," as the late Harvey Pack liked to say.

Comments and Conversation

April 26, 2022


anthony, can you email me the dosage index numbers for each derby contender, and tell me where I can find the info to perform the dosage calculations…Im a math head lol thanks

May 2, 2022


I’m looking for the dosage index profile for all horses in the 2022 derby, would deeply appreciate this. Thank you, sue

May 5, 2022


Great info Thank you

Is the dosage index profie online anyway for derby? It used to be easy to find. I can find the dosage but not the full profile. Also looking for earnings per start. Thanks in advance

May 8, 2022

Anthony Brancato:

You can consult the following web site to obtain complete dosage information on any horse:

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