What Factors Make The Most Impact On Finding Horse Racing Winners?

This is arguably the most complex question anyone can ask when it comes to horse racing. There are dozens of potentially relevant factors and hundreds of irrelevant ones when it come to horse racing.

Commonly used factors include:

  • Form
  • OR
  • Course & Distance
  • Going
  • Speed
  • Weight
  • Trainer/Jockey
  • Class
  • Days Since Last Ran
  • Odds

And many more! In fact, I’ve written extensively on most of these factors in ‘How to Choose the Right Factor Every Time in Horse racing’.

Today, I’m going to focus on Going, Class, OR and Days Since Last Ran (DSLR) and use Pool Impact Value (PIV) calculations to discover if these factors are worth considering when trying to find winners. Before reading on, I would recommend reading Michael’s articles on calculating Impact Value and Pool Impact Value. They are relatively short pieces but give you a clear insight into why you should use these calculations in the first place.

In a nutshell, you’re looking for a PIV figure of above 1 as this means horses are winning more than what you would expect on average.

For the record, all data comes from 2012-2016.


Going is often believed to be one of the most crucial factors in horse racing. To make things interesting, I looked at the performance of horses that ran their last race under the same official ‘Going’ description. So under ‘Firm’ for example, this relates to horses that also ran on Firm ground in their previous race.

Going Bets Wins Strike Rate PIV
Heavy 8879 1100 12.39% 0.85
Good 41047 4537 11.05% 0.86
Good to Firm 20508 2424 11.82% 0.84
Good to Soft 11862 1348 11.36% 0.87
Soft 17219 2064 11.99% 0.86
Standard 63833 7502 11.75% 0.86


You’ll notice that quite a few conditions are not represented here; that’s because there was insufficient data to draw a conclusion. What we can see above is that betting on horses which ran on the same type of ground the previous race is not a particularly good betting factor.

I then decided to see how favourites fared using the same criteria and the PIV’s were as follows:

  • Heavy: 0.94
  • Good: 0.91
  • Good to Firm: 0.91
  • Good to Soft: 0.97
  • Soft: 0.93
  • Standard: 0.94

As you can see, there is an improvement across the board yet none of the PIV figures even reach 1.00.

Finally, I took a look at the performances of favourites on the same Going as their last win. For example, if Horse X is running on Heavy ground and his last win was also on Heavy ground.

  • Heavy: 0.96
  • Good: 0.91
  • Good to Firm: 0.9
  • Good to Soft: 0.89
  • Soft: 0.92
  • Standard: 0.97

While there are a myriad of other criteria you could use, the data above suggests that Going is not necessarily as important as you might think when choosing winners. None of the above provides you with a PIV value above 1 which means under performance.


Once again, I’ll start with the performance of favourites but this time we’ll divide them into Class.

Class Bets Wins Strike Rate PIV
1 1961 699 35.65% 0.95
2 2290 640 27.95% 0.90
3 4368 1402 32.1% 0.92
4 11466 4129 36.01% 0.93
5 12768 4629 36.25% 0.95
6 7918 2722 34.38% 0.94


While favourites manage to achieve a PIV rating of at least 0.9, none of them make the magical 1.00 barrier.

The next step is to look at the performance of horses that are in the first four positions in the betting. Here are the PIV figures by Class:

  • Class 1: 0.91
  • Class 2: 0.89
  • Class 3: 0.9
  • Class 4: 0.91
  • Class 5: 0.89
  • Class 6: 0.89

The PIV figures here actually go down! Finally, I looked at the performance of horses that were either dropping one or two classes. For example, horses in Class 4 races that ran in Class 2 or Class 3 races last time out.

  • Class 2: 0.88
  • Class 3: 0.87
  • Class 4: 0.91
  • Class 5: 0.88
  • Class 6: 0.85

While I’m certainly not suggesting that Class isn’t an important factor, the data above at least shows it may not necessarily be a profitable one by itself.

Official Rating (OR)

OR is used in handicapping to ensure each horse is theoretically equal. Of course, the handicappers don’t always get it right and savvy punters can cash in heavily when the experts make a rare error. But can you see profits from using OR alone?

It was tricky to come up with a set of criteria so I ultimately decided to see how horses within certain OR ranges performed in a certain Class of race. The following is a fairly small sample of OR ranges but will hopefully be enough to paint a somewhat clearer picture.


OR Class Strike Rate PIV
51-59 6 10.31% 0.87
60-65 6 12.66% 0.86
71-79 4 10.98% 0.85
80-85 4 13.28% 0.88
91-99 2 8.09% 0.81
100-105 2 8.31% 0.86


I went through All-Weather races using the above criteria and the PIV remained below 1.00.

National Hunt

OR Class Strike Rate PIV
75-85 5 10.25% 0.88
86-95 5 10.88% 0.85
115-125 3 12.09% 0.85
126-135 3 14.66% 0.9


While it is again an admittedly small sample of data, we can surmise that Official Rating isn’t a particularly profitable factor on its own.

Days Since Last Ran (DSLR)

This is an interesting metric as it can indicate if a horse performs better after a quick return or a lengthy lay off. I’ve divided it into the three codes.

National Hunt

DSLR Bets Wins Strike Rate PIV
1-6 4640 709 15.28% 0.96
7-14 30538 3221 10.55% 0.84
15-30 73005 8293 11.36% 0.86
31-60 45421 5119 11.27% 0.87
61+ 49890 4651 9.32% 0.82


DSLR Bets Wins Strike Rate PIV
1-6 8724 1257 14.41% 0.94
7-14 46230 5027 10.87% 0.84
15-30 68235 7709 11.3% 0.87
31-60 27645 2863 10.36% 0.86
61+ 29045 2656 9.14% 0.83


All Weather

DSLR Bets Wins Strike Rate PIV
1-6 5146 848 16.48% 0.97
7-14 26630 3095 11.62% 0.84
15-30 36135 4096 11.34% 0.85
31-60 16637 1749 10.51% 0.85
61+ 17574 1730 9.84% 0.84


Unfortunately, there isn’t a single instance of a PIV of 1 or more. However, you can see a clear trend here. The PIV when betting on horses that had their last run in the 1-6 day range is by far the highest across the board.

I decided to analyse the performance of favourites who had run within the last 6 days (over all codes) and found the PIV to be 1.00. While National Hunt and Flat favourites had a PIV of 0.99, All-Weather favourites had a PIV figure of 1.02. All Weather favourites under these criteria also gave you a ROI of 3.28% at SP prices and a nice 8.24% ROI when using Betfair.

From this we can see that All-Weather favourites who last ran in the 1-6 day bracket perform slightly above expectations.


After lengthy research, it seems as if there is no single factor out of the four I’ve looked at that’s likely to lead to long-term profits. DSLR appears to be the most important factor on its own and it would be wise to focus on horses that have run within the last week.

This doesn’t mean you should ignore the factors above, it just means you need to combine them in order to find winners and more importantly, profit. It is further confirmation that there is no ‘magic’ factor in horse racing and if you believe anyone who says there is, I have a bridge I’d like to sell you!

Patrick Lynch

Patrick graduated from the National University of Ireland, Galway with an MA in Literature and Publishing but decided he would rather have the freedom of a freelance writer than be stuck in a publishing house all day. He has enjoyed this freedom since 2009 and has written thousands of articles on a variety of topics but sports betting is his passion. While his specialty is finding mismatches in obscure football leagues, he also likes to use his research skills to provide punters with detailed winning strategies in horse racing. You can check out his personal blog on or Twitter @pl1982 where he writes content to help small businesses achieve success.


  1. Is there a flaw in the method of calculating PIV in that SPs are used, these are not an indication of winning success as the bookmakers margin is included in the figures? As an example in a two horse race where the horses have an identical chance the true odds of wining for each horse are 50%. However the bookies will offer let’s say 5/6 which on your calculations would give the odds of winning of 55%. Therefore using a PIV of 1 as a benchmark is not correct and possibly explains why all the PIVs are less than 1.

    1. Sorry for the delay in replying Michael. As you say there is also a margin to take into consideration when using SP odds, this will kick the figures out slightly. However we know that SP figures do (including bookmaker margins) give a very accurate probability on a horse’s chance of success. If you replace the SP with Betfair SP, this will be even more accurate as the over-rounds are tiny in comparison. Without doing a direct side-by-side comparison I wouldn’t be able to tell you the exact difference taking bookmaker margins into account would have, but would not expect it to be huge. However, I can be very confident it wouldn’t push any of the above stats to a PIV of above 1, primarily because this is already taken account of in the market heavily.

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