The Kelly criterion answers the question every trader gets wrong: how much should I bet? Originally derived for gambling and information theory, it prescribes risking a fraction of capital equal to your edge divided by the odds. Bet more and you risk ruin; bet less and you leave growth on the table.
In its simplest form, the Kelly fraction is f = (bp − q) / b, where p is your probability of winning, q = 1 − p is the probability of losing, and b is the payoff ratio. The result is the share of your bankroll that maximises long-run compounded growth.
Full Kelly is aggressive — its swings are larger than most traders can stomach — so practitioners commonly use "fractional Kelly" (e.g. half-Kelly) to cut volatility at a small cost to growth. The key insight survives: size positions in proportion to your edge, not your conviction.
Sintinel applies Kelly-style sizing so a stronger, better-corroborated signal earns a larger suggested allocation, with hard caps to prevent any single name from dominating the portfolio.