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Rugby betting tips powered by our machine-learning Algorithm.

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History and Development

Our first forays into betting were cautious. We didn’t immediately bet the farm on the output of the Algorithm the very first weekend. And a good thing too. It would have been horrendous. Certainly marriage ending for myself. 

We’ve developed and tried many different strategies over the years, each one an improvement on the last until we meet the present day iteration. Here we’ll talk you through the development of our strategies and how each was discarded and improved in turn.

The below strategies were tried and tested over the course of just over a year (September 2019 to November 2020) over 814 matches and 17 different leagues or events, both international and domestic.

As a summary, the iterative strategies tried and discussed below were:

    1. Just betting on the favourite;
    2. Finding value bets;
    3. Using the Kelly Criterion to determine pot size;
    4. Fine tuning Kelly;
    5. Further tuning of Kelly.

Hopefully this serves as a guide for everyone as to how this works, no doubt for experienced bettors it may seem simplistic, but the idea was to explain in simple terms how we arrived at our present day strategy in such a way that everyone can understand and trust.

So, to begin ...

Strategy 1: Just Betting On The Favourite

Often people ask if we just bet on the favourite in each match, as indicated by the Algorithm. This ends up down, and you can see how this approach would have fared over the last year below. 

The graph below shows how your total pot size would have varied with different strategies of betting on the favourite. The orange shows betting 5% of your pot each time on the favourite, the blue 20% and the grey 50%. The smaller pot size performs best, but ultimately is failing and sits at £20 at the end of the experiment.


Essentially this approach fails for various reasons, but the easiest description would be the familiar expression ‘the house always wins’. Basically the bookies have the odds stacked in their favour. If you convert the bookies odds into percentages, you can see that they all add up to over 100%, on average around 107%. This 7% can roughly be thought of as the bookies profit. It basically means that they are inflating each team’s chances of winning, and therefore will pay less than they ought to if they win.

This strategy was abandoned fairly quickly as a result …


5% Pot Finish £20 -80%

20% Pot Finish £0 -100%

50% Pot Finish £0 -100%

Strategy 2: Value Betting

Therefore, you need to identify the situation when the bookies have mispriced  matches, and bet on those matches. What this means in layman's terms is that the bookies are paying out too much on one team, relative to our predicted likelihood of it coming off.

For example: the bookies have a match priced at 6/1, which gives an implied chance of 14.3%. However, the Algorithm gives the side a 20% chance of victory. This means, in the Algorithm’s eyes, that side will win 1 in 5 times, but that the bookies are paying out at the price of 1 in 7 times and therefore, over the course of enough matches, you should end up up.

The mathematical formula is:

Expected Value = (Expected Return * Prob. Win) - (Loss * Prob. Losing)

Here’s how this strategy would play out over the same course of matches.


The larger bet sizes are volatile and tend to 0 fairly quickly, which is unsurprising. Strategies that bet too large a percentage of pot size per bet will generally quickly lose money. However, betting 5% of your pot each bet seems to yield (just) a positive return over the time period (3% seems to be the optimum for this strategy), so there is clearly something in value betting and it forms the underlying principle of our strategies below. 


5% Pot Finish £103 +3%

20% Pot Finish £15 -85%

50% Pot Finish £0 -100%

Strategy 3: Kelly - Optimising For Value

So we need to explore this value strategy a bit more in order to maximise the returns from it. The Kelly Criterion is just such a thing - a scientific method for maximising pot returns over time.

This is explained more fully in the link above and elsewhere on the internet but, in essence, it looks at the amount of mispricing in a match AND the likelihood of the outcome, to determine the size bet that you should make in order to maximise your returns.

The mathematical formula is:

% Pot = (Expected Return * Prob. Win) - Prob. Losing

                                       Expected Return

This is the percentage that you see around the website, and in our emails and graphics - the amount of your total 'pot' that you should bet in each match.

Let’s see how this performs over time.


Not too bad. However, you can see that the ‘Full Kelly’ strategy also tends to 0 over time. This is because, despite Kelly’s claims to maximising returns over time, it is also maximally aggressive, i.e it aims to maximise returns at the fastest possible rate and in doing so, runs the risk of also losing quickly, especially if played over an infinite number of matches.

Therefore, most people usually opt for a fractional Kelly (betting a fixed fraction of the amount recommended by Kelly) for a variety of practical reasons in order to reduce volatility. You can see that a 20% fractional bet in orange generates a good, relatively consistent, return over time. We will use fractional bets going forwards in our example as the full, maximally aggressive, strategies always tended to 0 over time.


Fully Kelly Finish £0 -100%

20% Kelly Finish £211 +111%

Strategy 4: Swelly - Fine Tuning Kelly

In investigating the detail behind Kelly’s performance, we discovered a few things that perhaps could enhance the returns. 

First up, we had a look at the extremely ‘risky’ matches. These were matches that one side was very heavily favoured over the other. A lot of these matches were identified as ‘value’ by Kelly, but largely just because when the numbers became very small, the relative difference between our predictions and the bookies became much larger. 

Practically speaking, this meant that Kelly was identifying lots of really, really long shots as value bets, but the chance of them coming off was miniscule - think Namibia beating New Zealand in Rugby World Cup. We might give them a 1% chance of doing so, and the bookies may be paying out at 500 to 1, which is correctly identified as value by the Kelly Criterion. However, it is very unlikely to happen.

Of course, it is possible that our sample size isn’t large enough to take advantage of these matches (just one coming off would generate enormous returns), which is why we colour code these matches as yellow in our recommendations. Technically they are value bets, but we wouldn’t recommend betting on them. (More on our colour coding can be found here.)

We fine tuned these thresholds (i.e the minimum chance we required a side to win in order to bet) by league and event in order to maximise our return. This strategy was nicknamed the ‘Swelly’, a nod to Kelly and the team member who developed it. 


10% Swelly Finish £188 +88%

20% Swelly Finish £277 +177%


Strategy 5: Grelly - Fine Tuning Swelly

Next we ‘experimented’ with the probability of winning that we fed into Swelly. Usually this would be the chance a side has of winning that particular match, but this was substituted with the chance of the prediction being correct (through error originally ... but hey, that’s how cornflakes and penicillin were invented!).

This yielded our best results yet, and was affectionately named the ‘Grelly’ after Kelly and the idiot who first coded the mistake.


This strategy works as it is looking more holistically at the chance the prediction will be correct, rather than the specifics of the match outcome. It also rather handily removes some of the annoying features that Kelly often turned out. For example, outrageously heavy bets were often recommended for relatively heavy favourites in matches, as it was often assumed they generally wouldn’t lose. However, speaking from experience, this wasn’t always the case … happily however, Grelly removes these large bets and instead recommends more appropriately apportioned bets across the board. A handy mistake to make.


5% Grelly Finish £297 +197%

10% Grelly Finish £695 +595%


So that’s it! I hope it makes sense and you roughly understand what goes into the betting recommendations that we make. Let us know if you have any questions.

We’re always developing here at 4Cast HQ, and next on the list is investigating tailoring and optimising some of the Grelly parameters by event, rather than overall, hoping to maximise the return from better performing events.

We are also looking at tipping handicaps as well, and should have that up and running shortly on the website.

The current performance can be seen here, along with a breakdown of the Algorithm’s return by event and over time. Fingers crossed we’re still up ...

See the success

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Got any questions? Get in touch!

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    Current strategy

    The bread and butter of Rugby4Cast is making predictions on the outcome of rugby matches - ultimately that is probably why you were on the site in the first place so this probably isn't news; we do this using a vast range of data predominantly quantifying the historical performance of teams.

    After making predictions we do a number of things with them; firstly we publish them on our website as well as on our social media feeds and secondly we use them to inform betting decisions and guide how we place money on games. The way we decide what games to bet on, and indeed how much money to place per bet, largely revolves around finding value in the odds offered by bookies.

    What is value?

    When a bookie offers odds on a match they are also offering a prediction of the likelihood of each team winning (plus a bit of an "overground" so that they always make a profit: remember the phrase the house always wins?). Value can be identified when there is some disparity between the implied percentage chance of a win from the odds and our own prediction - for whatever reason we think the bookies might be missing something and either giving a team too much or too little chance of winning.

    How to identify value?

    To find value bets you need two things, firstly the odds a bookie is offering and secondly a prediction - here at R4C we conveniently have both of those things! In fact we go one better and have the odds from a huge number of bookies. We use these to identify value according to our take on the Kelly Criterion. 

    Is that it?

    Yes and no - the above is the basis for a lot of what we do, however we have done a lot of work and augmented the simple value tactic with further data and optimisations per each league we make predictions, likewise we have odds data from a large number of bookies so make sure we always have the best odds.

    Perhaps most importantly … does it work?!

    Yes! You can see the success of this current approach below; overall and split across time, leagues and specific matches. 

    See the success

    Given the tactic implemented it is important to understand that this is a long term strategy; we often tip the underdog and if you want the chance to generate the consistent returns we have been seeing then you will need to stick around and make all the recommended bets each week.

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      Kiwis! Looking for the best bookmakers to subscribe to? See https://mybettingsites.com/nz/

      Using the Algorithm

      As simple as we can ...
        • Decide your pot total for the weekend;
        • Check out the green recommended matches in the 'Recommended Bets' section, and review accordingly*;
        • Check Oddschecker or other comparison sites to see if any better odds have become available since we scraped the information;
        • Bet your desired percentage of your pot at the bookie offering the best price on the sides colour coded green by the Algorithm;
        • Check out any yellow matches and see if you fancy your chances;
        • Ignore the reds.

      That's it! Hopefully that makes sense, but please let us know if not.

      *by review accordingly, we mean to use your intuition to assess what you think of the recommendation. The Algorithm takes into account a wide variety of factors when making the recommendations, but it isn't foolproof. It will identify what it thinks are mispricings by the bookies, but if you disagree, then don't bet! Or reduce your % to something you are more comfortable with.

      Our success pages show what would happen had you bet exactly as the Algorithm had recommended, but it is almost certainly possible a human/algorithm combo would be more successful. To that end, the percentage recommendations should probably be thought of as a 'maximum' amount to bet. Ultimately, you need to choose something you are comfortable with.

      Colour coding

      We show our tips in 3 different colours on the website which are meant to guide you in deciding your risk appetite. 


      A green bet is a bet that has been identified as value, and the side in question has a greater chance of winning than our minimum threshold. These are recommended matches to consider bet on.


      A yellow bet is a bet that has technically been identified as value, but the side in question has less than our required minimum % chance of winning.

      The reason for this is that sometimes value bets are identified, but the side has a miniscule chance of winning, with the bookies pricing them with even less chance. This is still a value bet, but the chances of it coming off are quite long that you would need to cover a lot of them in order to end up up - something not everyone may wish to do, hence these bets are tagged as yellow.

      Depending on your risk appetite you may or may not wish to bet on these matches.


      A red bet is a bet that has no value. The bookies have this match priced similarly to The Algorithm and therefore there is no value in betting on it. Avoid these.

      Strategy and Percentages

      This is the specific recommendations on how much to bet based on our take on the Kelly Criterion (explained more fully here). 

      Simply put, it looks at the amount of mispricing in a match AND the likelihood of the outcome, to determine the size bet that you should make.

      This is the percentage that you see in the strategy - the amount of your total 'pot' that it is recommended you should consider betting on each match.

      Please let us know if anything is unclear by getting in contact below.

      A few other things / FAQs ...
      • Please gamble responsibly. If you are doing this to make a quick profit, or looking for guaranteed winners, this is probably not the thing for you. Don't gamble what you are not prepared to lose, and don't come crying to us if your bet doesn't come off - we cannot guarantee any returns. After all, this is sport - and that's why we love it!

      • If you disagree with the prediction and/or the tip - then don't bet! The Algorithm looks at a wide variety of things before a match in order to determine the likely outcome, but it doesn't take into account everything, and it's entirely possible that it may be wrong. If you think the prediction is out, and therefore the tip, then use your intuition on top of the recommendations to decide your course of action. Humans and machines working and thinking together very often produce better results that either operating alone.

      • Do you guarantee these tips / advice / that I will make money? No, obviously not. Ultimately, this can be thought of a little like investing in financial markets under the advice of an experienced investor. We have a strategy and take 'advice' from the Algorithm, which we think gives us an edge over the rest of the market. Indeed, at the moment, this appears to be true (see our success page). However, this may not continue, and we can place no guarantees on future profits. Similar to financial advice ("the value of your investment may go down as well as up") - and despite being a predictions site! - we don't actually know what will happen in the future. We think it will continue, and see no reason why our strategy will stop working, but we just can't guarantee that for sure.

      • Why don't you just keep quiet and do this yourself? We do use these to bet ourselves, and we are quite significantly up at the moment. However, we see no reason we can't also sell these tips to others as well! Also, rugby betting markets are quite thin and very large bets would skew the markets quite a lot, so opportunities would quickly become limited. Plus, some of our accounts are beginning to be capped on their activity. We're unsure at this stage whether it is because we are successful, or if it is just a blanket policy across certain leagues, but either way, our opportunities are limited doing this solo.

      What's included?

      Calculations of value for each match, identifying the tipping points at which you should consider placing money.

      Comparisons between bookmakers' odds, identifying the best bookie for each game.

      Recommendations on how much to stake, based on how mispriced the bookies are, and the likelihood of the outcome.
      ...plus more features coming soon.
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