Kelly Criterion Calculator
Kelly criterion calculator works out Decimal odds and American / moneyline odds from Odds, Odds format and Your estimated win probability. The default figures on this page give kelly stake of 100; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
6 steps
- Decimal price = 2, i.e. 100 American, 1/1 fractional, 50% implied.
- A stake of 100 returns 200 in total, a profit of 100.
- b = decimal - 1 = 1, p = 0.55, q = 0.45.
- f* = (bp - q)/b = (0.55 - 0.45) / 1 = 0.1
- Full Kelly stakes 10% of the bankroll: 100.
- The break-even probability at this price is 50%, so the edge is 0.1 per unit staked.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the kelly criterion calculator calculates
Converts between American, decimal, fractional and implied-probability odds, works out payouts and parlay returns, strips the bookmaker margin to give no-vig fair prices, finds arbitrage stakes across books, sizes a bet by the Kelly criterion and computes hedge stakes and martingale sequences.
How to use this kelly criterion calculator
Enter Odds, Odds format, Your estimated win probability and Bankroll. Decimal odds updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Decimal odds, American / moneyline odds and Fractional odds.
The method follows Kelly, J.L. Jr (1956), "A New Interpretation of Information Rate", Bell System Technical Journal 35(4), 917-926, Thorp, E.O. (2006), "The Kelly Criterion in Blackjack, Sports Betting and the Stock Market", Handbook of Asset and Liability Management, Elsevier, Cortis, D. (2015), "Expected values and variances in bookmaker payouts: a theoretical approach towards setting limits on odds", Journal of Prediction Markets 9(1), 1-14 and Shin, H.S. (1993), "Measuring the incidence of insider trading in a market for state-contingent claims", The Economic Journal 103(420), 1141-1153.
What you can compare
Change one input at a time to see how it affects Decimal odds, American / moneyline odds and Fractional odds. The inputs you can vary are Odds, Odds format, Your estimated win probability, Bankroll and Kelly fraction.
Understanding Decimal odds, American / moneyline odds and Fractional odds
This is an arithmetic tool, not betting advice. Bookmaker prices already carry a margin, so the long-run expected value of a bet at posted odds is negative unless you genuinely have an edge. Gamble only what you can afford to lose.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
What is the Kelly Criterion formula?
On the figures this page opens with, the kelly stake is 100. No single number fits everyone: it follows Odds, Odds format and Your estimated win probability, so enter your own above and the answer updates as you type.
What should my Kelly multiplier be?
Converts between American, decimal, fractional and implied-probability odds, works out payouts and parlay returns, strips the bookmaker margin to give no-vig fair prices, finds arbitrage stakes across books. On this page it is computed from Odds, Odds format and Your estimated win probability and shown as Decimal odds, American / moneyline odds and Fractional odds.
What is the formula for calculating the Kelly Criteria decimal odds?
It needs Odds, Odds format, Your estimated win probability, Bankroll and Kelly fraction. Nothing else is required, and the figures stay in your browser.
What is the Kelly calculator?
The result gives Decimal odds, American / moneyline odds, Fractional odds, Implied probability, Hong Kong odds and Indonesian odds, each labelled with its unit so the figure can be read on its own.
Does Warren Buffet use Kelly Criterion?
Converts between American, decimal, fractional and implied-probability odds, works out payouts and parlay returns, strips the bookmaker margin to give no-vig fair prices, finds arbitrage stakes across books. Put your own figures in above and the working updates beside the result. For scale, the default figures on this page give 100.
How accurate is the Kelly Criterion?
The kelly criterion calculator follows the stated method, but the result is only as reliable as Odds, Odds format, Your estimated win probability, Bankroll and Kelly fraction and the assumptions shown. Check the working and sources before relying on it for an important decision.