The A/E Statistic In Horse Racing

The A/E statistic in horse racing is also known as the Actual vs. Expected ratio. It is a measure commonly used to assess the profitability of betting selections.

This statistic helps bettors and analysts evaluate how well a particular set of criteria or factors predicts the actual outcomes of horse races.

The formula for A/E is quite straightforward. As it equals Actual Winners divided by Expected Value.

Here's a breakdown of the components:

Actual Winners:
The number of times the selected set of horses have won their races.

Expected Value:
The number of winners you would statistically expect based on the chosen criteria.

When the A/E number greater than 1, it suggests that the selected criteria are performing better than expected. Indicating potential value in those selections. 

Conversely, an A/E number below 1 implies that the selections are underperforming compared to what would be expected statistically.

How to work out the expected winners value.

It is clear that the actual winners will equal the number of winners in a set of results but what about the expected value?

For the expected value we use the odds of all runners and turn these odds into a percentage chance and then make the calculation.

So to get the percentage chance from the odds you can use SP and add 1 to get the decimal odds. Or use the Betfair odds, which we do in our results. Then divide 100 by this number to get the percentage chance.

So a horse with Betfair odds of 5.0 would have a 20% chance of winning. As 100/5 = 20.

A horse with Betfair odds of 16 would have a 6.25% chance of winning. As 100/16 = 6.25.

Once you have all of the odds you can work out the percentage chance of each run and total this up to get the expected value.

Let us say we have a set of results that produce the following 5 results.

Won 2/1, Lost 4/1, Won 6/1, Lost 3/1 and Lost 2/1.

Adding 1 to each SP to get the decimal odds, we can work out that the expected value would be:

2 + 1 = 3. 100 / 3 = 33.33%, then 25%, 16.66%, 20% and 33.33%. Divide the total of the percentages by 100 and you have 1.28.

With the final calculation being Actual Winners divided by Expected Value. You get 2 / 1.28 = 1.56

As you have seen already, any A/E value over 1 is a positive. In fact something as large as 1.56 is quite rare. But of course these are made up numbers, plus we have only used five results for this example.

The larger the set of the results, the more accurate your A/E value will be, so bear this in mind.

Simplifying this process for your betting.

If you want to find out if your set of results has an A/E value above or below 1, then it would be a mammoth task to work out the expected value for a set of 100, 500 or 1000 results.

Our system builder can help with this. As it calculates the A/E value for every set of system results that you test or are using.

The image below is from a system you can download and read more about on another one of our recent blog posts called, Finding Big Priced Winners.

As you can see, the A/E value for this set of 2,412 results, is 1.27, so very positive indeed.

The A/E Statistic in Horse Racing Inform Racing

Of course the system builder updates this number every time you add more results. So you can see at all times how your results are performing.

In practical terms, punters can use A/E values to assess the profitability of different factors. Such as speed ratings, trainer or jockey performance, or other relevant factors.

A value significantly above 1 may indicate that the set of criteria are identifying horses that outperform the market expectations. Presenting a potential betting opportunity, or long term profitability.

Here are some additional points and considerations related to the A/E statistic in the context of horse racing analysis:

  1. Contextual Analysis:
    • A/E values should be interpreted in the context of the specific criteria or factors being analysed. For example, an A/E value for a particular trainer or jockey might be more meaningful when considering specific race conditions or types of races.
  1. Sample Size Matters:
    • The reliability of A/E values increases with a larger sample size. It's essential to consider a sufficient number of races or instances when calculating A/E to reduce the impact of random fluctuations.
  1. Dynamic Nature of A/E:
    • A/E values are not static and can change over time. As racing conditions, horse form, and other variables evolve, it's important to regularly assess and update A/E calculations for ongoing accuracy. This is something that the system builder will do for you automatically.

Video example.

As mentioned previously, the A/E number is an ideal way to see how jockeys have been performing over the previous months and years.

On this video I have taken a look at some jockeys, to see how the A/E value compares between them when riding the fancied horse and those that start a bigger prices. 

A few of these may surprise you as those considered 'at the top' do not have such good A/E values as you may have expect them too.

It also shows you a few ways that you can look at a set of results, or in this case, the results from any jockey and then drill down into a few form factors to see where they perform the best, or the worst.

You can watch the video on YouTube  here >>


It must be said that the A/E statistic in horse racing, is one of the most underrated data sets that many don't even use.

It is even more important than the overall profits made from a system or a set of results. And by using the Inform Racing system builder, the A/E statistic or value, is automatically calculated for you, for every set of results, or data test, such as you will have seen on the video above. 

By knowing how a set of results out performs or under performs by looking at the A/E value, you will be way ahead of those who just see a big profit figure and think they have found the holy grail.