Kelly criterion calculator
At a 52.5% chance (your 55.0%, shrunk toward the market's no-vig 50.0%), the bet’s expected value is +0.23% per dollar staked, and the price breaks even at 52.4%. The Kelly stake is the share of the bankroll that edge supports; it shows once you are signed in.
The Kelly criterion sizes a bet by its edge: the stake is the edge divided by the odds, as a share of the bankroll. Kelly first shrinks your chance toward the market’s no-vig chance, because a guess is rarely as sure as it feels. Type the price, your chance it wins, your bankroll and, if you have it, the other side’s price. Anyone sees the expected value; the stake shows once you are signed in.
- Expected value
- +0.23%
- per dollar staked, at the chance below
- Chance used
- 52.5%
- your 55.0%, shrunk toward the market's no-vig 50.0%
- Break-even
- 52.4%
- the chance the price needs
- Stake
- Sign in
- your stake shows once you are signed in
Questions about the kelly criterion calculator
What is the Kelly criterion?
A rule for how much of a bankroll to stake on a bet with an edge: more when the edge is bigger, less when the price is longer, and nothing when there is no edge. Staked that way, a bankroll grows fastest over many bets without going broke.
Why does Kelly shrink my chance toward the market?
The market’s no-vig price is a strong estimate, and most people’s own chances are too confident. Kelly blends yours halfway toward the market’s before sizing, so a mistaken edge costs less. Without the other side’s price there is nothing to shrink toward, and your chance is used as typed.
Why is the stake only shown when signed in?
A stake is advice about your own money, so Kelly shows it only to signed-in members who have set their bankroll and limits. The expected value and the chance used are the same for everyone.
What is fractional Kelly?
Staking a fixed share of the full Kelly stake, often a half or a quarter. It grows a bankroll a little more slowly but with far smaller swings, and it forgives an overestimated edge.
What does negative expected value mean?
At the chance used, the price pays less than the bet is worth, so on average it loses money. Kelly stakes nothing on a bet like that.