Bankroll Management

Bankroll management is the practice of: 1. Defining a separate "betting bankroll" (money you can afford to lose entirely) 2. Sizing each bet as a small percentage of the bankroll 3. Adjusting size up/down as the bankroll grows/shrinks

Standard sizing: 1-2% per bet, called "1 unit." A 5-unit bet (5%) is a strong opinion. Anything over 10% is reckless even with a huge edge.

Why this matters: variance can destroy even profitable bettors who bet too big. A bettor with a true 55% win rate at -110 (about +5% ROI) can still go bankrupt if they bet 20% of bankroll per bet, because a normal losing streak compounds catastrophically. The same bettor at 2% sizing is extremely unlikely to bust.

Kelly criterion is the mathematical answer to "optimal" sizing given a known edge. In practice, fractional Kelly (quarter or half) is safer because edges aren't perfectly known.

SportsBookISH's Skill Score includes a Sharpe-style return-per-volatility metric that implicitly rewards good bankroll management. Bets that are too large relative to ROI variance hurt the score.