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Discipline & Risk
The Kelly Criterion, Explained
The formula for how much to bet to grow fastest - and a warning about what 'optimal' actually feels like.
NoVo Options Trading · 2026
The Kelly criterion is a formula that calculates the bet size which maximizes long-run capital growth, given your edge and odds. In simple form it weighs your win probability against your payoff ratio to produce a percentage of capital to risk. It's the mathematical answer to "how much should I bet?"
How it works
Kelly says the optimal fraction to risk rises with your edge and your payoff, and falls as your edge shrinks. A big, reliable edge justifies larger bets; a thin edge justifies small ones. With no edge, Kelly says bet nothing - which is itself a useful discipline.
Why full Kelly is brutal
Here's the catch: "optimal for growth" is not "comfortable to trade." Full Kelly produces enormous drawdowns - swings that would shake almost anyone out or trigger a ruinous losing streak if your edge estimate is even slightly off. And edge estimates are always uncertain. Full Kelly assumes you know your odds precisely; you never do.
Full Kelly is mathematically optimal and practically unbearable. That's why nobody trades it.
Fractional Kelly
The practical answer is fractional Kelly - betting a half or a quarter of what the formula suggests. This sacrifices a little theoretical growth for a large reduction in volatility and blow-up risk, and it cushions the error in your edge estimate. It's the same logic behind conservative position sizing: survival first, growth second. Bet small enough that being wrong about your edge can't end you.
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NoVo is a software tool for market analysis and for executing trades you initiate, not financial advice. This article is general education, not investment advice. Options trading involves substantial risk of loss, up to and including your entire capital. NoVo makes no guarantee of profit, win rate, or performance, and past results do not predict future outcomes. You are responsible for your own broker account, configuration, and trading decisions.