Kelly's Criterion Calculator

What is the Kelly Criterion?

The Kelly Criterion is a position-sizing framework that helps you decide how much to stake on a bet when you believe you have an edge. In plain English: if your estimated probability of winning is better than the sportsbook’s price implies, Kelly tells you the optimal stake (as a % of bankroll) to grow your capital over the long run. The classic Kelly Criterion formula is f* = (bp − q) / b, where b is decimal odds minus 1, p is your true win probability, and q = 1 − p.

Use the Kelly’s Criterion Calculator above: enter your Fair Odds (your edge) and the current Sportsbook Odds. Set a Kelly’s Multiplier to run full or partial Kelly and the tool will output your recommended stake and % of bankroll.

How to use the Kelly Criterion (sports betting)

  • Estimate fair odds (your true probability). This can come from a model, market making, or sharp price signals.
  • Compare to sportsbook odds. If fair odds < sportsbook odds (in decimal), you likely have positive expected value.
  • Choose a Kelly fraction. Full Kelly = max growth but higher volatility. Many pros use 0.25×–0.50× Kelly for smoother swings.
  • Stake only from your bankroll and update your model as new info arrives.

Kelly Criterion betting vs. “zero risk” myths

Kelly is not a zero risk betting strategy. It maximizes long-term growth if your probabilities are accurate, but you will still experience variance. That’s why fractional Kelly is popular—trading a bit of growth for better risk control.

Why investors love it

The idea behind Kelly—betting more when the edge is larger—has influenced investors and portfolio managers for decades (you’ll often see Warren Buffett mentioned in discussions about disciplined, edge-based capital allocation). In sports betting, the logic is identical: size your positions based on probability and edge, not emotion.

Quick FAQ

How to calculate Kelly Criterion?

Convert sportsbook odds to b = decimal − 1, estimate p, then compute f* = (bp − (1 − p)) / b. The calculator handles this for you using Fair Odds vs Sportsbook Odds.

How to use Kelly Criterion in betting?

Only apply it when you have a genuine edge (positive EV). Set a partial Kelly multiplier (e.g., 0.5×) to reduce drawdowns and keep stakes consistent with your bankroll policy.

Kelly Criterion vs. “criteria” — which is correct?

Criterion is singular; criteria is plural. Here we’re talking about one rule—so Kelly Criterion is correct.

Pro tip: Kelly assumes your edge estimate is accurate. If your model is noisy, use a smaller multiplier (e.g., 0.25×–0.50×) and cap maximum stake per bet.

This Kelly Criterion sports betting guide is for education only. Wager responsibly and never risk funds you can’t afford to lose.