A bankroll is a budget rather than a strategy. Its purpose is to make the size of a losing run survivable and to decide the question of when to stop before the question becomes emotional.
The right size depends far more on variance than on edge. A player betting even money at 1% can sit for a long evening on relatively little; a player chasing 35:1 payouts needs many times that to see a normal number of swings without going broke first.
The one durable rule is that bankroll should be decided before you sit down and treated as the cost of the evening. Money you would mind losing does not belong in it.
Progressive betting systems are usually sold as bankroll management and are the opposite: they concentrate risk into rare catastrophic sessions rather than spreading it. See martingale.
Where the numbers come from
Related terms in odds & money
- House edge — The average share of each bet the casino expects to keep over the long run.
- RTP — Return to player: the mirror of house edge, quoted as what comes back rather than what is kept.
- Expected value — The average result of a bet if it could be repeated indefinitely.
- Variance — How widely results scatter around their expected value.
- Standard deviation — A measure of how far results typically stray from the average.
- Unit — One standard bet, used as the yardstick for measuring results and bankroll.
Where an entry quotes a number, that figure comes from the computed sections of this site rather than from another glossary, so the definition and the derivation cannot drift apart. Each entry links to the page where the number is worked out.