Bet Sizing Helper
Calculate optimal bet size based on your bankroll and risk tolerance. Use Kelly Criterion for mathematically optimal sizing when you have an edge.
Calculate Bet Size
Your total available capital for betting (must be greater than 0)
Maximum percentage of bankroll to risk (1-5% recommended)
How It Works
📊 Risk-Based Sizing (Simple)
The basic approach: Bet a fixed percentage of your bankroll (1-5% recommended for most bettors). This provides simple, consistent risk management without requiring market analysis.
Formula: Bet Size = Bankroll × Risk Percentage
🎯 Kelly Criterion (Advanced)
The Kelly Criterion calculates optimal bet size based on your edge (the difference between your estimated probability and the market price). It maximizes long-term growth while managing risk.
Formula: Kelly % = (bp - q) / b
where b = odds, p = your probability estimate, q = 1 - p
🛡️ Half-Kelly (Recommended)
Full Kelly can be aggressive. We use half-Kelly (50% of the Kelly fraction) for safety, which still provides excellent long-term growth with reduced volatility.
💡 Example
Scenario: $10,000 bankroll, 2% risk tolerance
Simple sizing: $200 bet (2% of bankroll)
With Kelly: Market price is 0.60 (60%), you estimate 0.70 (70%)
Your edge: 10% advantage
Full Kelly: ~15% of bankroll ($1,500)
Half Kelly: ~7.5% of bankroll ($750)
Final bet: $200 (respecting your 2% risk limit)
⚠️ Important Guidelines
• Never bet more than you can afford to lose
• Start with low risk percentages (1-2%) until experienced
• Kelly Criterion assumes accurate probability estimates - be honest about uncertainty
• Consider using even smaller fractions (quarter-Kelly) for extra safety
• This tool provides mathematical guidance, not financial advice
• Account for trading fees and slippage in your calculations
📈 When to Use Kelly
Use Kelly Criterion when:
✅ You have researched the market thoroughly
✅ You believe you have information others don't
✅ You can accurately estimate the true probability
✅ You're betting with an edge, not gambling
Stick to simple risk-based sizing when:
❌ You're unsure about your probability estimate
❌ You're new to prediction markets
❌ You want consistent, conservative bet sizes