Kelly stake calculator
Given a price and your own probability, how much of the bankroll does Kelly say to stake?
- Break-even probability at this price
- 47.62%
- Your edge per unit staked
- 5.00%
- Full Kelly stake (% of bankroll)
- 4.55%
- Suggested stake
- 11.36
Kelly sizes a bet to grow a bankroll fastest if your probability is right. It is very sensitive to that estimate, which is why most people use a quarter or less. This is arithmetic, not advice.
How it works
The Kelly fraction is (p × b − q) ÷ b, where p is your win probability, q is 1 − p and b is the decimal odds minus 1. At evens with a 60% chance that is (0.6 − 0.4) ÷ 1 = 20% of the bankroll. If p is at or below the break-even probability (1 ÷ decimal odds) the answer is zero: no edge, no bet.
Full Kelly assumes your probability is exactly right, and nobody's is. A quarter of the Kelly stake gives up a little growth for a lot less variance, which is why quarter Kelly is the default here and the cap our own scanner works under.
The hard part is p. The calculator takes your number at face value; where that number comes from is the whole game.