It’s simple math. The more horses you have in a race, over a substantial sample size, the less likely the favorite is to win. When you have more horses to beat, the favorite is less likely to reach the winner’s circle. Even if you were not great in math in school, it’s easy to understand this concept.

This is one of the major reasons that the best contest / tournament players in the horse racing world will focus on races with full fields (typically, that means 12 horses in the race). Some of them do this, whether they realize it or not, by focusing their plays on turf races, which tend to have fuller fields as compared to most dirt races.

According to Ed Derosa of Horse Racing Nation, these were the favorite win rates based on field size through the first eight months of 2024:

4-5 horses. 46.5%

6 horses: 42.4%

7 horses: 39.5% – right at the national average for favorite win rate

8 horses: 35.8%

9 horses: 35.2%

10 horses: 32.6%

11 horses: 30.6%

12 horses 32.0%

13 horses 40.0% (much smaller sample size)

14 horses: 0% (12 races)

So, how does field size affect the favorite win rate? A lot.

What about Favorites at Certain Tracks?

Ed also listed the top 5 tracks with 200 races or more that had the lowest favorite success rate. Not surprisingly, these were mostly tracks that often have large field sizes. Two tracks, Woodbine and Turfway, have synthetic race tracks which also coincides with larger field sizes.

Oaklawn Park 34.4%

Century Mile in Canada 32.9%

Saratoga Race Course 32.3%

Woodbine in Canada 31.0%

Turfway Park 30.5%

Over a reasonable sample size, races with large fields tends to have a smaller success rate for the public choice, aka favorite. Shorter fields equate to a much higher win percentage for favorites.

Keep reading: What is the Success Rate for Favorites in Horse Racing?