Definition
Bankroll is the total capital set aside exclusively for betting, kept separate from living expenses. Proper bankroll management prevents ruin during losing streaks that will occur even with a true edge. Standard recommendation: no single bet should exceed 2–5% of total bankroll (flat-betting) or Kelly-calculated fraction. Bankroll grows only from betting profits, never from reloading after losses. Starting bankroll determines maximum unit size and position sizing ceiling.
Worked Example
Bankroll: $2,000. Max flat bet at 2%: $40 per bet. After 50 bets with 55% win rate at −110: 27.5 wins × $36.36 = $1,000 profit; 22.5 losses × $40 = $900 lost. Net: +$100. Bankroll grows to $2,100. New 2% unit: $42. Never bet $200 because "I'm on a hot streak" — that's how $2,000 becomes $0.
Why It Matters
Bankroll discipline is the difference between surviving variance and going broke. A bettor with a 5% edge but no bankroll discipline will go bust before the edge materializes over enough bets.