How to use the Kelly Criterion in Betting + Free Calculator!

Any punter know that it is usually unwise to bet their whole bankroll or a huge portion of it on a single bet. However, how much should you bet? Managing your bankroll is the most important part of betting strategy. Betting too much can have an adverse effect on your bankroll, especially on a losing streak, while betting too little on a win streak means wasted opportunity. While certain players simply trust their instincts, there are a number of bankroll management strategies that rely on mathematical formulas. These will help you decide how much to bet on any given bet. The most important is the Kelly Criterion. It does not follow a fixed betting pattern or percentage. Instead, it instructs you to bet according to your estimation of value. The higher the value, the bigger the percentage of your bankroll you should bet.

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What is the Kelly Criterion?

The Kelly Criterion is a formula that helps you calculate how much you should bet. It recommends that you should only bet if there is a difference between the true odds (your estimated odds) and the given odds (the bookie’s odds). Though it may seem complicated, the formula is actually very simple.

Kelly Criterion Formula for Sports Betting

The Kelly Criteria has several versions. Here is the simplest version for sports betting:

f* = [(b x p) – q] ÷ (b)

• f is the fraction of the bankroll to bet
• b are the decimal odds – 1
• p is your estimated probability of winning
• q is the estimated probability of losing (1 – p)

Kelly Criterion Football Example

You can easily use the Kelly Criterion to decide how much to bet on a football match. Let us say that Manchester United is set to play against Real Madrid for the final of the Champions League. The odds makers have set Real Madrid as a slight favourite, at odds of 1.82. In this case, there is no draw possible (We will bet on match winner, not result after 90 minutes). These odds imply a 55% chance of winning. However, based on your own analysis, you believe Real Madrid has a 65% chance of winning.
You have seen value, so you can now use the Kelly Criterion to decide how much of your bankroll to bet.

• b = 1.82 – 1 = 0.82
• p = 0.65
• q = 0.35
• f*= [(b x p) – q] ÷ (b) = [(0.82 × 0.65) – 0.35] ÷ 0.82 = 0.2231

The Kelly Criterion implies you should bet 22.31% of your bankroll on Real Madrid.

Kelly Criterion Horse Racing example

The Kelly Criterion also works for horse race betting. Let us say that your horse (Let us call him Lucky Punter) gets 4/1 odds (or 5.0 in decimals, or a 20% implied probability of winning) at the Cheltenham Hurdle. You believe, based on careful analysis, that Lucky Punter actually has a bigger chance of winning. You estimate the chances slightly higher, at 25%.

Using the Kelly Criterion, you can now calculate how much of your bankroll to bet on Lucky Punter.

• b = 5.0 – 1 = 4
• p = 0.25
• q = 0.75
• f*= [(b x p) – q] ÷ (b) = [(4 × 0.25) – 0.75] ÷ 4 = 0.0625

The Kelly Criterion implies you should bet 6.25% of your bankroll on Lucky Punter.

Kelly Criterion Calculator

We are giving you two options on how to use the Kelly Criterion Calculator. You can either download our excel version or else just use our online version. Take your pick below!

Download Kelly Criterion Calculator

Download our free and easy-to-use Kelly Criterion Calculator by downloading this excel file! All you need to do is choose which column you want to use (depending whether you want to input your odds in fractions, decimal or american format) and follow the instructions provided!

Use Our Online Kelly Criterion Calculator

If you prefer using a quick online version, then try our own online Kelly Criterion Calculator! It is very easy and quick to use. Just follow the instructions below!

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How to use the Kelly Criterion to decide how much of your bankroll to bet

As you can see, the Kelly Criterion does an effective job at telling you how much to bet. Sometimes, it can instruct you to bet an amount that is much more that what you would like to bet intuitively. In that case, you can opt to use the Half Kelly or the Fractional Kelly.

Half Kelly

The Half Kelly is a more conservative strategy. Simply calculate the Full Kelly and divide by two.

Fractional Kelly

The Fractional Kelly lets you use any fraction of the full Kelly you want. Use a third, a fourth or a fifth, or whichever fraction best suits your betting strategy.

Combining with other staking strategies

You can easily combine the Fractional Kelly with any positive or negative staking strategy. That would mean you increase or decrease how much of a Full Kelly you bet, depending on your win/loss streak. Combine it with the Fibonacci Betting System, or Martingale System, for example.

When not to bet

When there is negative value, or the oddsmakers see the odds of an event more likely than you do, the Kelly Criterion suggests you should not bet. The formula will give you a negative number. Of course, that could mean that precisely the opposite outcome has more value, which is something you could consider betting on.

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Advantages and disadvantages of using the Kelly Criterion

The Kelly Criterion has several advantages for the modern Punter, though it has its limitations.

Advantages

The Kelly Criterion has a proven track record, and is used by top investors and punters all over the world. Here are several advantages for punters.

Safeguard your bankroll

It helps you safeguard your bankroll, while taking just the right amount of risk. By increasing your wager and not simply betting the same amount every time, you have a dynamic betting strategy.

Keep your greed in check

The system is easy to use, and can protect you from your own bullishness. Instead of betting the bank on what you believe is a ‘sure win’ (sure wins do not exist in most sports), you are forced to rely on a smart formula that limits how much of your bankroll you risk.

Know when not to bet

The Kelly Criterion easily lets you know when not to bet. If it throws up a negative number, then it is time to reconsider your bet or even place the opposite bet.

Disadvantages

While the Kelly Criterion has many advantages, it has several drawbacks.

Based on your calculations

Whether or not the system works in the long term depends on your own skill at finding the right bets. If your estimations are better than the oddsmakers, it can be a great way to beat the bookies. If not, your wins will depend on luck.

A potentially aggressive strategy

The Kelly Criterion can potentially be a very aggressive strategy. It can easily instruct you to bet as much as 20% of your bankroll on a single bet. Most professional punters usually bet less than 5% of their bankroll per wager. Therefore, only bet a larger percentage is you are very sure you have identified value.

How to create your own Kelly Criterion Calculator in Excel

Creating your own Kelly Criterion Calculator in Excel is very easy. Just follow these simple steps.

1. Open a new Excel spreadsheet and create these headers:

• Bankroll (How much is your total Bankroll?)
• Kelly Staking Fraction (Which percentage of a Full Kelly do you want?)
• Outcome 1 (Name the outcome)
• Outcome 2 (Name the outcome)
• Odds of 1 (The odds offered by bookies)
• Odds of 2 (The odds offered by bookies)
• Probability of 1 (How likely do you estimate Outcome 1?)
• Probability of 2 (How likely do you estimate Outcome 2?)
• Stake on 1 (How much should you bet on Outcome 1?)
• Stake on 2 (How much should you bet on Outcome 2?)

2. Enter your bankroll and staking fraction (How much of a full Kelly do you want to bet?)

3. Enter the two possible outcomes for the market in 1 outcome and 2. Also, place the market odds in Odds of 1 and Odds of 2. For this example, we will use the odds from our earlier hypothetical matchup between Real Madrid and Manchester United for the Champions League final. (In this case, there is no draw)

4. Fill in your own estimated probabilities for each outcome

5. Add formulas to Stake on 1 and Stake on 2

• Paste this formula in H2

=((((E2*G2)-1)/(E2-1))*A2)*B2

• Paste this formula in I2

=((((F2*H2)-1)/(F2-1))*A2)*B2

As you can see, our 50% Half Kelly is exactly half of our earlier calculation for the Full Kelly.

6. Let’s see how it works for our Horse Racing example.

As you can see, you only need to put odds in for one side of the outcome. Drag the cross cursor down in I2 to get the same formula for I3.

History of the Kelly Criterion

The Kelly Criterion was originally developed by economist John Kelly, who was working at AT&T's Bell Laboratory. It was developed to analyse long distance signal noise issues. The method was published in 1956 as “A New Interpretation of Information Rate”. Soon after it was published, it became popular among big investors. Warren Buffet, Charlie Munger, as well as legendary bond trader Bill Gross, all recommend the method. It helps them decide how much to invest in any given project.

The gambling community later realized its potential as an optimal betting system for horseracing as well as other sports. It is a general money management system for financial investments as well as sports betting.

John Kelly first proposed the Kelly Criterion (Image: Public Domain)

Kelly Criterion Experiment

The Kelly Criterion has been proven to work in several experiments. This includes an experiment where players could bet on a coin that would land on head 60% of the time, for an even money bet. 28% of the players actually went bust, while only 21% of the players reached the maximum. By using the Kelly Criterion, and betting 20% of their total bankroll, players had a 94% chance of reaching the maximum.

ThePuntersPage Final Say

Your success as a punter will depend on your choice of bets. However, as demonstrated by John Kelly, the size of your bets, relative to your bankroll, is very important.

Using Bankroll management strategies such as the Kelly Criterion will not guarantee spectacular returns. However, it will help you limit your losses, protect you from being too bullish and help you decide how much of your bankroll to wager on each bet. Read our article on Bankroll Management for more tips.

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