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Kelly Criterion Calculator

Recommend optimal bet size based on win rate and R:R.

Inputs

Win probability

Reward-to-risk ratio (avg win / avg loss)

Bankroll (optional)

Fractional Kelly (%)

The Kelly Criterion helps determine the optimal fraction of capital to wager to maximize long-term growth.
Inputs: win probability (p) and reward-to-risk ratio (R = average win / average loss).
Full Kelly can be aggressive. Many practitioners use fractional Kelly (e.g., 50%) to reduce volatility and drawdowns.
If the Kelly fraction is negative, your edge is likely unfavorable; the model suggests not betting.