Antes increase the size of the pot before anyone has acted, which makes stealing more profitable and forces the game open. Cash games with antes play considerably looser than the same stakes without.
Tournaments introduce them at later levels for exactly that reason: as blinds rise relative to stacks, antes accelerate the pressure and stop play becoming a fold-fest.
The big blind ante, now standard in most tournaments, has one player post the whole table's ante in a single chip. It speeds the game up considerably and changes nothing about the arithmetic.
The size relative to the big blind is what determines the effect. An ante of a tenth of the big blind barely registers; an ante equal to it transforms the game, since the pot before any voluntary action is now large enough that folding relentlessly loses faster than playing badly. Modern tournament structures use that deliberately to force action as stacks shorten.
Related terms in poker
- Pot odds — The price a call is getting, compared against how often it needs to win.
- Outs — The cards remaining that would improve your hand to a likely winner.
- Equity — Your share of the pot, meaning how often you win it if the hand plays to showdown.
- Implied odds — The money you expect to win later if your draw comes in, beyond what is in the pot now.
- Position — Where you act in the betting order, and the largest structural edge in poker.
- Button — The dealer position, which acts last on every postflop street.
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.