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Kelly Criterion Bet-Sizing Tool
The Kelly Criterion is a mathematical formula used to determine the optimal size of bets when you have a statistical edge. Named after John Larry Kelly Jr., who developed it at Bell Labs in 1956, this tool helps maximize long-term growth while managing risk in sports betting scenarios.
Kelly Criterion Bet-Sizing Tool
Calculate optimal bet sizes using the Kelly Criterion for maximizing long-term growth while managing risk
Input Parameters
Your estimated probability of winning (0.55 = 55%)
Your total betting bankroll in dollars
Fraction of Kelly to bet (0.25 = 25% of Kelly, recommended)
Include long-term bankroll growth projections
Quick Scenarios
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Examples
Practical Examples
Example 1: NFL Point Spread
- Your Estimate: 58% chance of covering spread
- Odds: -110 (1.91 decimal)
- Implied Probability: 52.4%
- Edge: 5.6%
- Full Kelly: 10.4% of bankroll
- Recommended (25% Kelly): 2.6% of bankroll
Example 2: Soccer Match
- Your Estimate: 35% chance of away team winning
- Odds: +280 (3.80 decimal)
- Implied Probability: 26.3%
- Edge: 8.7%
- Full Kelly: 7.4% of bankroll
- Recommended (20% Kelly): 1.5% of bankroll
Example 3: No Edge Scenario
- Your Estimate: 48% chance of winning
- Odds: -110 (1.91 decimal)
- Implied Probability: 52.4%
- Edge: -4.4% (negative)
- Recommendation: Avoid this bet
Tips & Best Practices
Professional Tips
Starting Out
- Conservative Approach: Begin with 10-20% of Kelly recommendations
- Track Performance: Monitor actual vs. expected results
- Gradual Increase: Increase Kelly fraction as confidence and experience grow
- Focus on Process: Emphasize consistent application over short-term results
Advanced Application
- Market Efficiency: Adjust expectations based on market sophistication
- Line Movement: Consider how odds changes affect your edge
- Closing Line Value: Use final odds as benchmark for probability accuracy
- Seasonal Adjustments: Modify approach based on sport-specific factors
Psychological Aspects
- Discipline: Stick to calculated bet sizes regardless of recent results
- Emotional Control: Don't chase losses or increase bets after wins
- Long-term Perspective: Focus on process over individual outcomes
- Regular Review: Periodically assess and adjust your approach
Conclusion
The Kelly Criterion is a powerful tool for optimal bet sizing, but it requires:
- Accurate Probability Estimation: The foundation of successful Kelly betting
- Disciplined Implementation: Consistent application regardless of short-term results
- Risk Management: Using fractional Kelly for practical application
- Continuous Learning: Regular assessment and adjustment of approach
When used properly with conservative Kelly fractions, this tool can help maximize long-term growth while managing downside risk in sports betting activities.
Remember: The Kelly Criterion is a guide, not a guarantee. Success depends on the accuracy of your probability estimates and your ability to maintain discipline in implementation.
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