Free calculator
Kelly criterion calculator
Enter the decimal odds, the probability you give the bet and your bankroll. The calculator returns the Kelly stake, the expected value and the break-even price.
Runs entirely in your browser; nothing you type is sent anywhere. For information only: PinnRadar sells odds data, takes no bets and gives no betting advice.
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Get a free key →How the Kelly stake is worked out
With decimal odds d, the net odds are b = d − 1. If you win with probability p and lose with q = 1 − p, Kelly stakes the share f = (b·p − q) / b of your bankroll. Example: odds 2.10 and a 52% chance give f = (1.1 × 0.52 − 0.48) / 1.1 ≈ 8.4%. At quarter Kelly that is about 2.1%.
When b·p is smaller than q the formula turns negative: the price is below fair value for your probability and Kelly says not to bet.
Getting a probability you can trust
Kelly is only as good as the probability you feed it. A common approach is to take Pinnacle’s price for the same market, remove the margin with the no-vig calculator, and use that as p when another bookmaker offers longer odds. The PinnRadar odds API streams those Pinnacle prices live, so the same calculation can run on every market in code.
Checking your results
Over a few hundred bets, results say little; the closing line value of your bets says more about whether your probabilities are sharper than the market.
Questions people ask
What is the Kelly criterion?
A staking formula that sizes each bet to grow a bankroll as fast as possible over the long run. It stakes more when your edge is bigger and nothing when the price offers no edge.
What is the Kelly formula?
f = (b × p − q) / b, where b is the decimal odds minus 1, p is your probability of winning and q = 1 − p. The result f is the share of your bankroll to stake.
Why do most bettors use fractional Kelly?
Full Kelly assumes your probability is exactly right. Small errors in the estimate lead to over-betting and large swings. Half or quarter Kelly gives up a little growth for much smaller drawdowns, which is why it is the common choice.
Where does the win probability come from?
From your own model, or from a sharp market. Many bettors use Pinnacle's no-vig price as the probability and stake Kelly when a softer bookmaker offers a better price.
Is this betting advice?
No. The calculator applies a formula to the numbers you enter. PinnRadar provides odds data and does not recommend bets.
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Feed these numbers from code
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