Mathematical Edge

The Kelly Criterion Calculator

The professional formula for "Optimal Bet Sizing." Calculate exactly how much of your account you should risk on a single trade to maximize long-term growth and avoid ruin.

Strategy Metrics

Win Probability

Reward-to-Risk (Odds)

$Total Account Size

Kelly Fraction (Aggressiveness)

Why Fractional Kelly?

Full Kelly is mathematically optimal but results in extreme volatility. Most professional traders use "Half Kelly" (0.5) or "Quarter Kelly" (0.25) to significantly reduce drawdown while maintaining a high growth rate.

Suggested Risk Position

$16.25%

$1,625 Total Risk

Edge Found

Expected Growth Per Trade

65.00%

Based on probability & odds

Full Kelly (Max Aggressive)

$32.50%

Trading Tip: To use the Kelly Criterion, you must have an accurate Win Rate. If your win rate is unproven, start with Quarter Kelly (0.25) to protect against "Estimation Error."

Mastering the Kelly Criterion

What is the Kelly Criterion?

Developed by John L. Kelly in 1956, the Kelly Criterion is a mathematical formula used to determine the optimal size of a series of bets. In trading, it helps you find the "Sweet Spot" between betting too little (slow growth) and betting too much (potential bankruptcy).

The Formula Explained

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

f*: The fraction of the bankroll to bet.
p: The probability of a win.
q: The probability of a loss (1 - p).
b: The odds (Reward-to-Risk ratio).

Why Professionals Use Fractional Kelly

The Full Kelly amount is the exact point that maximizes the growth rate but carries high risk. If your win probability is slightly overestimated, Full Kelly can lead to Ruin.

By using Fractional Kelly (Half or Quarter), you sacrifice a small amount of growth for a massive reduction in volatility and drawdown. It is the "Insurance Policy" used by professional blackjack teams and quantitative hedge funds.

Key Takeaway:

If the formula returns a negative number, it means the trade has a Negative Expectancy. In this case, the optimal bet size is zero.

This calculator is part of our advanced library of cryptocurrency calculators. Explore the fullCrypto Trading Toolsto optimize your strategy and manage risk like a professional.