The Kelly criterion answers the question that comes after finding value: how much should I stake? Its formula — edge divided by odds-minus-one — commits a fraction of your bankroll proportional to how big your advantage is and how likely the bet lands.
Say you have 2.20 on a coin flip that is truly 50/50: fair odds 2.00, so you hold a real edge. Kelly says stake (0.5 × 2.20 − 1) ÷ (2.20 − 1) ≈ 8.3% of your bankroll. Better odds or higher probability push the fraction up; a smaller edge shrinks it towards zero.
Two lessons hide in the formula. First: when your edge is zero, Kelly says stake zero. Betting without an edge is not entertainment with upside — it is scheduled donation, and no staking plan, martingale or "system" changes that. Second: even with a real edge, Kelly stakes are startlingly small and full Kelly is a rollercoaster. Most professionals use a quarter or half Kelly, accepting slower growth for survivable swings.
We publish edge sizes rather than stake advice — but Kelly is the honest lens for reading them: a 3% edge justifies a small, disciplined bet, not a bankroll-defining plunge. Anyone who tells you otherwise is selling variance as certainty.
See how we apply this on every match in our methodology. Methodology →
See these ideas at work in our public track record — every call logged before kick-off, losses included.