What Does Overround Mean in Horse Racing?

When placing bets on horse racing, some fundamentals are used by every bookmaker to ensure that they are protected, and one of these factors is overround. No matter if you are someone who studies all horse racecards before the race begins, the overround factor is a part of how bookmakers make sure they come out ahead, no matter who wins.

Here at Racing TV, we are going to look at what the overround is, how it works and how it affects horse racing betting.

In horse racing, overround refers to the bookmaker’s profit margin. This is a calculated edge built into the odds to ensure the bookmaker profits from bet markets, regardless of the race outcome.

Essentially, the combined implied probability of all the horses winning in a race adds up to more than 100%. That extra percentage is the overround, and this is where the bookmaker makes their profit.

To understand this, we have created this table, which shows how the overround works:

Total = 104.4%

As the implied probability is over 100%, the extra 4.4% is the overround, and this is the bookmaker’s profit margin to ensure they make a profit.

For bettors, understanding the overround can provide an extra insight into how good or bad a market is in terms of the offered odds.

✅Low Overround (e.g 102%) = Better Value

❌High Overround (e.g 120%) = Worse Value

Markets with lower overrounds are typically more competitive, often found:

An understanding of overround can be essential to getting the best value from horse racing bets, so we have a formula that you can use to calculate this value.

Implied Probability (%) = (100 ÷ Decimal Odds)

For example, if a horse was placed at 5/2, they would have the decimal odds of 3.5. By dividing 100 by 3.5, you will get the answer of 28.57, which is the implied probability for that horse.

By doing this for every horse in the selection, you can work out if the selection has good or bad value. The higher the percentage, the worse the value.

By determining whether the selection has a high or low overround, you can compare it between bookmakers to see which one offers the best value. By calculating the overround value, you can use this technique alongside the best horse racing tips to not only find top-quality horses, but also find the very best odds for them.

Whilst finding better value consistently can be useful, this does not guarantee that the bets you place will return, so it is something that should be taken into account, but not relied on.

Most casual bettors don’t notice overround, but it affects every bet you place. Bookmakers aren't just offering odds; they’re managing risk and ensuring a profit. And overround is their insurance policy.

So next time you're studying the odds before a race, take a second to consider the overround. It won't guarantee you a win, but it might help you spot better value, bet smarter, and lose less in the long run.

If you are fascinated by the sport and want to watch horse racing live, there is no better place than Racing TV, and the site is also home to in-depth guides and horse racing reviews.