The Kelly criterion
Once you have an edge, the next question is how much to stake. Kelly turns your edge and the price into the bet size that grows a bankroll fastest — without betting yourself broke.
What Kelly actually optimises
Kelly sizes each bet to maximise the long-run growth rate of your bankroll, not the profit on any single wager. Bet too little and you leave growth on the table; bet too much and a normal losing streak ruins you.
It needs just two inputs — your estimated edge and the odds. The bigger the edge and the longer the price, the larger the fraction it tells you to stake.
Why almost everyone bets fractional Kelly
Full Kelly is only optimal if your probability estimate is perfect — and it never is. Overestimate your edge and full Kelly turns dangerously aggressive.
Half- or quarter-Kelly keeps most of the growth while cutting volatility and drawdowns sharply. It's the standard professionals actually use.
Kelly across a portfolio
Real bettors hold many positions at once, sometimes correlated. Applying full Kelly to each in isolation ignores that overlap and over-stakes the book.
Yoseri sizes every signal with fractional Kelly and caps exposure across correlated positions, so the maths stays disciplined automatically.
Theory is nice. Edges pay.
Yoseri does the pricing, edge and bankroll math for you — free to start, no card.