Sizing

/edge 0.45 0.55                     Calculate edge (prob - price)
/edge "Trump 2028" --estimate 0.55  Edge vs market price

TypeScript API Reference

Create Sizing Calculator

import { createSizingCalculator } from 'clodds/sizing';

const sizing = createSizingCalculator({
  // Bankroll
  bankroll: 10000,

  // Kelly fraction (1 = full, 0.5 = half)
  kellyFraction: 0.5,

  // Limits
  maxPositionPercent: 25,
  maxTotalExposure: 80,
});

Basic Kelly

// Binary outcome (YES/NO market)
const size = sizing.kelly({
  marketPrice: 0.45,        // Current price
  estimatedProb: 0.55,      // Your probability estimate
  bankroll: 10000,
});

console.log(`Optimal bet: $${size.optimalSize}`);
console.log(`Edge: ${size.edge}%`);
console.log(`Kelly %: ${size.kellyPercent}%`);
console.log(`Expected value: $${size.expectedValue}`);

Fractional Kelly

// Half Kelly (recommended for most traders)
const halfKelly = sizing.kelly({
  marketPrice: 0.45,
  estimatedProb: 0.55,
  bankroll: 10000,
  fraction: 0.5,  // Half Kelly
});

// Quarter Kelly (very conservative)
const quarterKelly = sizing.kelly({
  marketPrice: 0.45,
  estimatedProb: 0.55,
  bankroll: 10000,
  fraction: 0.25,
});

console.log(`Full Kelly: $${sizing.kelly({...}).optimalSize}`);
console.log(`Half Kelly: $${halfKelly.optimalSize}`);
console.log(`Quarter Kelly: $${quarterKelly.optimalSize}`);

Multi-Outcome Kelly

// For markets with 3+ outcomes
const multiKelly = sizing.kellyMultiOutcome({
  outcomes: [
    { name: 'Trump', price: 0.35, estimatedProb: 0.40 },
    { name: 'DeSantis', price: 0.25, estimatedProb: 0.20 },
    { name: 'Haley', price: 0.15, estimatedProb: 0.15 },
    { name: 'Other', price: 0.25, estimatedProb: 0.25 },
  ],
  bankroll: 10000,
  fraction: 0.5,
});

for (const alloc of multiKelly.allocations) {
  console.log(`${alloc.name}: $${alloc.size} (${alloc.percent}%)`);
}

Portfolio-Level Kelly

// Optimal allocation across multiple markets
const portfolio = sizing.kellyPortfolio({
  positions: [
    { market: 'Trump 2028', price: 0.45, prob: 0.55 },
    { market: 'Fed Rate Cut', price: 0.60, prob: 0.70 },
    { market: 'BTC > 100k', price: 0.30, prob: 0.40 },
  ],
  bankroll: 10000,
  correlations: correlationMatrix,  // Optional
  fraction: 0.5,
});

console.log('Optimal Portfolio:');
for (const pos of portfolio.positions) {
  console.log(`  ${pos.market}: $${pos.size}`);
}
console.log(`Total exposure: ${portfolio.totalExposure}%`);

Confidence-Adjusted Sizing

// Reduce size when less confident
const size = sizing.kellyWithConfidence({
  marketPrice: 0.45,
  estimatedProb: 0.55,
  confidence: 0.7,  // 70% confident in estimate
  bankroll: 10000,
});

// Size is reduced proportionally to confidence
console.log(`Confidence-adjusted size: $${size.optimalSize}`);

Edge Calculation

// Calculate edge
const edge = sizing.calculateEdge({
  marketPrice: 0.45,
  estimatedProb: 0.55,
});

console.log(`Edge: ${edge.edgePercent}%`);
console.log(`EV per dollar: $${edge.evPerDollar}`);
console.log(`Implied odds: ${edge.impliedOdds}`);
console.log(`True odds: ${edge.trueOdds}`);

Risk-Based Sizing

// Size based on risk per trade
const size = sizing.riskBased({
  bankroll: 10000,
  riskPercent: 2,     // Risk 2% per trade
  stopLossPercent: 10, // 10% stop loss
});

console.log(`Position size: $${size.positionSize}`);
console.log(`Max loss: $${size.maxLoss}`);

Kelly Fractions

Edge Requirements

Formulas

Kelly Formula

f* = (p * b - q) / b

Where:
f* = fraction of bankroll to bet
p = probability of winning
q = probability of losing (1 - p)
b = odds received (1/price - 1)

Edge Formula

Edge = Estimated Prob - Market Price
EV = Edge * Bet Size

Best Practices

1. Use fractional Kelly — Full Kelly has too much variance
2. Be conservative on edge — Overconfidence kills accounts
3. Account for correlation — Don't over-expose to same theme
4. Set max position — Never more than 25% in one market
5. Reassess regularly — Edge changes as prices move