Kelly Criterion Calculator
Optimise Your Betting Stake
Welcome to the Kelly Criterion Calculator, your go-to tool for determining the optimal bet size that maximises the expected growth of your betting bankroll.
The Kelly Criterion is a powerful mathematical formula that helps value bettors decide how much to stake based on their bankroll, odds, and probabilities.
Whether you're betting on events with no lay options or using advanced strategies like value betting, this tool ensures that you’re balancing growth and risk for long-term profitability.
What Is The Kelly Criterion?
The Kelly Criterion is a staking strategy designed to maximise the growth rate of your bankroll over time. It's especially useful when you’re dealing with value bets - situations where you have an edge, such as overpriced selections from bookmakers or "no lay" strategies like Extra Place offers.
This system calculates the optimal stake based on:
- Your bankroll size: The total amount you have to bet.
- The odds of the bet What the specific odds of the bet are.
- The fair odds: What the true probability of the bet winning is.
By calculating the precise stake size, the Kelly Criterion helps you avoid the extremes of over-betting (which risks losing your bankroll too quickly) and under-betting (which limits your long-term gains).
Why Use The Kelly Criterion Calculator?
When using a method like Matched Betting, you're usually laying bets at an exchange to lock in a profit. But if you venture into value betting or betting without a lay, calculating the correct stake size becomes critical. The Kelly Criterion makes sure you're betting enough to maximise growth, but not so much that a string of losses could wipe out your entire bankroll.
Our Kelly Criterion Calculator simplifies this process and helps you quickly calculate your optimal stake size, ensuring you’re betting smart while managing risk.
What Is Fractional Kelly Staking?
The Kelly Criterion can sometimes recommend stakes that are relatively large. While betting the full Kelly stake maximises your bankroll’s growth, it can be more volatile and riskier.
That’s why many bettors use fractional Kelly staking, where you bet only a percentage (e.g., 50% or 25%) of the Kelly-recommended stake. This approach balances your long-term growth with reduced risk, protecting your bankroll from big swings in variance.
For example:
- Bankroll: £1,000
- Bookmaker odds: 5.0
- Fair odds: 4.0 (representing a 25% chance of winning)
Using the Kelly formula, the recommended stake might be £62.50. With fractional Kelly staking set at 25%, you would bet £15 instead, significantly lowering your exposure to risk while maintaining a solid growth rate.
How to Use the Kelly Criterion Calculator
Using the Kelly Criterion Calculator is simple:
- Enter your bankroll amount: This is the total amount of money you have available for betting.
- Input the Kelly percentage: Enter the percentage Kelly staking you wish to use (e.g., 25%, 50%). (25% Kelly staking recommended).
- Add the bookmaker’s odds: The odds provided by the bookmaker for the event you’re betting on.
- Probability of winning/Fair odds: Enter the probability of the bet winning as a percentage or the fair odds as a decimal figure (e.g., 25% for the probability of the bet winning or 4.0 for the fair odds).
Once you’ve entered all the information, the calculator will display your optimal stake size, ensuring you're betting the right amount for consistent bankroll growth.