A unit is a standardized measure of bet size relative to your bankroll. Using units normalizes performance tracking, makes record-keeping comparable across bankroll sizes, and enforces consistent bet sizing discipline.
Defining a unit: Most bettors set 1 unit = 1-2% of starting bankroll. On a $1,000 bankroll, 1 unit = $10-20. Professional bettors often use 0.5-1% as their standard unit due to the variance in sports outcomes.
Consistent unit sizing benefits: - Win rate and ROI become meaningful metrics (% return per unit) - Prevents emotional over-betting after wins or chase bets after losses - Makes bankroll projections calculable (expected growth given edge and volume)
Variable unit systems: Some bettors use tiered units (0.5, 1, 2, 3 units) for different confidence levels. This is only valid if the confidence tiers correspond to actual edge differences — not just feeling. Larger units should require documented model signals, not intuition.
Kelly vs. flat: Kelly Criterion is the mathematically optimal sizing formula for confirmed-edge bettors. Flat sizing (always 1 unit) is safer when edge is uncertain. Fractional Kelly (25-50% of full Kelly) is the practical middle ground for most model-based bettors.
Tracking in units: Record every bet in units. Calculate ROI as: (Total Units Won − Total Units Wagered) / Total Units Wagered × 100%. Industry standard: 5% ROI per unit wagered is elite; 2-3% is solid; break-even is 0%.