What does the Kelly criterion calculate?
It calculates the bankroll fraction that maximizes long-run logarithmic growth when the supplied win probability is accurate.
Full, half or quarter Kelly
Kelly criterion calculator for bet size.
Use your own probability estimate and the listed odds to calculate a full, half or quarter Kelly bankroll fraction.
Full Kelly8.33%
Selected fraction4.17%
Calculated stake$41.67
Expected return per $1+12.50¢
A $0 result means your probability estimate does not show a positive mathematical edge at these odds.
How it works
Your probability drives the answer.
Kelly compares your estimated win probability with the break-even probability implied by the odds. A positive gap produces a bankroll fraction; no positive gap produces a $0 result.
The formula is extremely sensitive to an inaccurate probability estimate. Fractional Kelly reduces the calculated stake, but it cannot make a bad estimate accurate.
What are half Kelly and quarter Kelly?
They use 50% or 25% of the full Kelly fraction to reduce the size and volatility of the calculated stake.
Why does the calculator recommend $0?
The probability you entered does not imply a positive mathematical expected return at the listed odds.