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CALCULATOR · KELLY

Kelly calculator

Free Kelly criterion and value calculator: enter the odds, your own estimate of the outcome probability and your bankroll to get the share of the bankroll, the stake, the expected profit (EV) and the fair odds. No sign-up; it all runs in your browser. For example, odds of 2.00, a 55% probability and a bankroll of 10,000 give a full Kelly of 10%, a half Kelly stake of 500 and an EV of +10%.

Odds
Outcome probability, %
Bankroll
Kelly fraction

Full Kelly 10.00 % · Share of bankroll 5.00 %

Stake 500.00

EV per unit staked 10.00 % · Fair odds 1.82

There is an edge: the expected profit is positive.

Settings
Odds format
Currency
Commission, %

Finding surebets by hand takes too long. The Dozor scanner compares bookmaker lines and shows surebets with the stakes already worked out.

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How to use the calculator

  1. Enter the odds of the bet and your own estimate of the outcome probability, in percent.
  2. Enter your bankroll and choose the Kelly fraction: full, ½ or ¼.
  3. Read the share of the bankroll, the stake amount, the EV and the fair odds.
  4. If the EV is not above zero, the formula gives a zero stake: there is no edge.

How it is calculated

The Kelly criterion picks the share of the bankroll that maximises capital growth for a win probability p and odds k: f = (p × k − 1) / (k − 1). The expected profit per unit staked is EV = p × k − 1, and the fair odds are 1 / p. If the EV is not above zero, the formula gives a zero stake. Example: k = 2.00, p = 0.55 → f = (0.55 × 2 − 1) / 1 = 0.10, EV = +10%, fair odds 1.82. On a bankroll of 10,000, full Kelly is 1,000 and half Kelly is 500. In practice people stake a fraction of Kelly (½ or ¼): the formula is sensitive to an error in the probability estimate.

What the calculator does not account for

  • The formula is only as good as your probability estimate: an overestimated probability gives an oversized stake, and at odds of 2.00 an error of 5 percentage points (0.55 instead of 0.50) wipes out the edge.
  • Kelly is designed for a series of independent bets with the same estimate; it guarantees no result for a single bet.
  • Bookmaker limits may be lower than the calculated stake.
  • The commission is set in the settings and reduces the effective odds.

The outcome probability is your own estimate. Line discrepancies between bookmakers, where a surebet needs no probability estimate, are shown in real time by the Dozor scanner.

FAQ

What is the Kelly criterion in betting?

It is a formula for the share of the bankroll to stake on a bet with a positive expected profit: f = (p × k − 1) / (k − 1), where p is the win probability and k the decimal odds. Example: k = 2.00 and p = 0.55 give 10% of the bankroll.

Why do people recommend half or quarter Kelly?

Full Kelly is sensitive to an error in the probability estimate and causes big swings in the bankroll. A ½ or ¼ fraction reduces drawdowns at the cost of slower growth.

How do you find a value bet?

A bet has value if your probability is higher than 1/k: then EV = p × k − 1 is above zero. The calculator shows the EV and the fair odds 1/p to compare with the quoted price.

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