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Determine the mathematically optimal stake size to maximise long-term bankroll growth while managing risk.
The Kelly Criterion balances Risk (loss probability) vs Reward (the odds).
1. Enter your total Current Bankroll.
2. Enter the Decimal Odds available (e.g. 3.0 for 2/1).
3. Enter your Estimated Win % — this is your edge. Be honest!
4. Select a Kelly Mode — Half Kelly is recommended for safety.
The biggest mistake most punters make is not picking the wrong horse — it is betting the wrong amount. You could pick winners all day but if you bet too little, your bankroll will not grow. If you bet too much, a short losing streak will wipe you out.
The Kelly Criterion solves this mathematically. It calculates the exact percentage of your bankroll to risk based on the edge you have over the bookmaker.
The calculator is only as good as the data you put in. You need to estimate the true probability of the horse winning — not the market implied probability.
Example: A horse is priced at 2/1 (3.0 decimal). The bookmaker is implying a 33% chance of winning. If your analysis suggests the horse actually has a 50% chance, you have a genuine edge. Enter 50% and Kelly will tell you exactly how much to bet to exploit that gap.
Know your stake — now use these tools to execute the strategy.
Disclaimer: This calculator is provided for educational purposes only. The Kelly Criterion is a mathematical formula for optimal growth but relies entirely on the accuracy of your estimated win chance. If you overestimate your edge the formula can suggest dangerous stakes. Always gamble responsibly and verify your own figures before placing any bets.