Unit Size Calculator

Units normalize bet sizing across different bankrolls. A bettor with a $500 bankroll betting 1 unit and a bettor with a $50,000 bankroll betting 1 unit are taking the same proportional risk, even though one is wagering $5 and the other $500.

Tracking results in units makes win-rate and profit comparable across bettors and across time. If you grow your bankroll from $1,000 to $1,500, your unit size grows from $10 to $15 — but "up 30 units" still describes your performance cleanly.

Flat unit sizing (always bet 1 or 2 units regardless of the bet) is simpler and easier to track. It's the right default for casual bettors and for anyone whose probability estimates aren't precise enough to differentiate one bet's edge from another.

Kelly sizing varies bet size by your edge. A bet with a 5% estimated edge gets sized larger than a bet with a 1% edge. Kelly maximizes long-run growth in theory but requires honest probability estimates and accepts more variance. Most serious bettors use half- or quarter-Kelly as a compromise. See what is Kelly staking? for the full formula.

The standard convention is to re-evaluate unit size when your bankroll changes by ±25% from where you started. If you start at $1,000 and grow to $1,250 (or shrink to $750), recalculate your unit size at the new bankroll level. This keeps your risk-per-bet proportional to your current capital, not your starting capital.

Avoid mid-session unit-size changes based on hot or cold streaks. The math of edge and variance doesn't care about your last 10 results; sizing changes should reflect bankroll changes, not emotional reactions to recent volatility.