Talking in units rather than currency makes results comparable across stakes. A player up forty units had a good session whether the unit was $5 or $500.
A unit is normally the table minimum or a fixed fraction of bankroll, commonly between 1% and 2%. The point of fixing it is that it removes the decision about bet size from the moment when you are least able to make it well, which is after a loss.
Flat betting means keeping the unit constant. It is unexciting and it is the only approach that does not quietly increase your exposure at the worst possible time.
The other reason to think in units is that it makes results honest across time. A player who moves from $10 to $25 bets after a good month has not necessarily improved; measured in units the record is comparable, and measured in currency it flatters the recent stretch. Almost every serious player's records are kept in units for exactly this reason.
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.
- Bankroll — The money set aside for gambling, kept separate from money needed for anything else.
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.