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Female Runners in Horse Racing

One aspect of horse racing that has had little coverage over the years from a stats based perspective is the performance of female horses. Female horses make up around a third of all racehorses and their age determines whether they are known as fillies or mares. Fillies are female horses aged 4 or younger; mares 5 or older.

It should be noted that in general male horses are slightly bigger (both weight and height wise) than female horses, which potentially will make a difference when they race each other.

I am going to dig down into the stats to see what I unearth.

For this article I have looked at UK racing over the most recent 7-year period from January 1st 2015 to December 31st 2021.

Any profits or losses quoted have been calculated to £1 level stakes using Betfair Starting Price (BSP) taking the 5% commission into account.

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In this article I will be analysing mixed sex races – races that are open for both male and female horses. There are female only races too and I may well revisit them in a later article.

Firstly, let us dig down into ALL mixed sex races on the flat and see the overall performance of males versus females:

Sex of horseBetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
Male runners2061012272711.00– £11738.20– 5.700.86
Female runners8652378889.10– £6371.15– 7.400.85

As we can see males have a higher strike rate and lose slightly less in percentage terms. A/E index figures though are almost identical.

So, despite the average physical edge for males, the difference in terms of performance and outcome is not perhaps as big as one might imagine.

Moving on, it is worth splitting this raw data up into turf races and all weather races as there is a difference. Let’s look at all weather races only first:

Sex of horseBetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
Male87993997011.30– £3064.05– 3.500.87
Female3996832888.20– £3473.33– 8.700.81

Males definitely have a strong edge here; everything seems to be in their favour – strike rate, ROI % and A/E index values. This initial data suggests that you may want to steer clear of all weather races if considering backing a female runner.

Despite my main focus being on female horses it should be noted that colts (‘entire’ male horses aged 2 to 4) score an impressive 16% of the time on the all weather.

In fact, 4yo colts have done extremely well during the period of study winning 261 races from 1414 runners (SR 18.5%) for a profit of £109.18 (ROI +7.7%). They have a very solid A/E index value too of 0.98.

The good news for female horses is that the turf results read a bit differently:

Sex of horseBetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
Male1181081275710.80– £8,674.10– 7.300.85
Female4655546009.90– £2,897.82– 6.200.88

The difference in strike rates between the two is now down to just 0.90% (compared with a 3.1% difference on the all weather), and females have performed slightly better than males in terms of return on investment.

In addition to this, female runners have the higher A/E index value. In turf races therefore the playing field looks fairly level.


Looking at the data so far, it seems sensible to focus our attention on turf mixed sex races as there seems to be parity when it comes to females versus males.

Age of female horse

I want to look at the age stats for females in mixed sex races to see if there is anything we can glean:

Female ageBetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
294719009.50– £838.62– 8.900.86
319351203710.50– £1,012.80– 5.200.89
492409019.80– £609.32– 6.600.86
542054169.90– £598.32– 14.200.91
6 or older42883468.10+ £161.24+ 3.800.86

From aged 2 to 5 the strike rates are very similar (all within 0.70%).

Those aged 6 or older have a lower strike rate but this is what one would expect and it happens with male runners also. The oldest group have made a profit but the figures are skewed somewhat by one big priced winner (Valentine Mist in 2019 won at the BSP of 403.65). Take that winner out and losses equate to around 5.50%.

So, nothing stands out here in reality.

When researching racing you have to be prepared that some data you dig down into gives you little or no edge.

Here is a case in point.

Handicaps / non handicaps

Time to examine whether females running in mixed sex races do better in handicaps or non handicaps:

Race typeBetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
Non Handicap1374113229.60– £2,056.62– 15.000.88
Handicap32814327810.00– £841.20– 2.600.88

Similar strike rates and exactly the same A/E index values. However, there is a big difference in the returns.

A loss of 15p in the £ in non handicaps compared with a loss of less than 3p in the £ in handicaps.

I decided to look at the results in more detail expecting to see that the handicap returns were skewed by some very big priced winners. As it turns out however, grouping together all the horses that started 100.00 BSP or bigger they actually made a significant loss of 19p in the £.

Indeed, if we focus in on female handicappers priced 45.00 BSP or lower this group of runners would have broken even at BSP – quite astonishing really considering there were 28,000 horses in that data sample.

The figures certainly seem to suggest you are better off focusing on handicaps if looking to back female runners in mixed sex events.

Time of Year

I have noted with some of my past research that certain fillies and mares seem to flourish in the summer months and hence I wondered if there was any general pattern with warmer weather producing better overall results.

I have grouped together female results from May to August and compared them with March, April, September, October and November.

(N.B no turf races between December and February):

MonthsBetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
March, April; Sept to Nov1432512508.70– £2,081.94– 14.500.85
May to Aug32230335010.40– £815.88– 2.500.89

As we can see it does seem the warmer weather brings out the best in fillies and mares. Better strike rate, a higher A/E index value and a significant improvement in the ‘bottom line’.


I next wanted to explore the performance of female favourites in turf mixed sex races. Here is what I found – the data includes clear and joint favourites combined:

Market rankBetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
Favourite4422140631.80+ £54.42+ 1.200.97

An overall profit which is surprising, but good to see nonetheless. Although profits of just over 1p in the £ is not going to make you a millionaire!

I did check all weather female favourites assuming they would not have performed so well due to the earlier data uncovered in this article. My hypothesis was correct with all weather favourites winning less often (SR 29.7%) producing losses of £202.20 which equates to a loss of 6.5 pence in the £.

The A/E index value was also lower at 0.89.

The pattern was replicated when I studied female second favourites in races open to both sexes.

On the turf second favourites were successful 20.1% of the time breaking even to BSP; on the sand the strike rate dropped to 18.9% with losses of over 5 pence in the £. Third favourites on the turf also outperformed their all weather counterparts breaking even once again to BSP.

Good recent run on the all weather

My final port of call was to check the following idea – with females finding it harder to win on the all weather, it may be that females who win a mixed sex race on the all weather are worth following next time.

Especially if switching to the turf.

As it turns out LTO all weathers switching to the turf next time would have produced a small profit as the table below shows:

BetsWinsSR %Profit / Loss (BSP)ROI % (BSP)A/E
4868016.50+ £43.82+ 9.001.01

Now the even better news – if you extend this idea to backing all females that finished in first 3 LTO in a mixed sex all weather race and then switch to race on the turf next time, we get the following excellent figures:

BetsWinsSR %Profit /Loss (BSP)ROI % (BSP)A/E
176525814.6+ £333.82+ 18.90.97

Excellent returns of nearly 19 pence in the £. Not only that these runners would have made a profit in 6 of the last 7 seasons which gives me more encouragement that this idea may continue to prove profitable in the future.


To conclude female runners can be competitive in mixed sex races. Here are the key bullet points from the research:

1.  Concentrate on turf races NOT all weather ones;

2.  In general, handicap races offer better value than non handicaps for female runners on the turf;

3.  May to August produce better results;

4.  A finish in the first three on the all weather last time out has been profitable if switching to turf next time;

5.  Female favourites on the turf have a good record.

I hope this article has been enlightening – it certainly has for me. Some interesting stats that I have been unaware of for too long!

David Renham  

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