What Is an Iso-Raise in Poker?

An iso-raise, short for isolation raise, is a preflop raise made over one or more limpers with the aim of playing the pot heads-up against them. You are not raising to take it down immediately — you are clearing the players behind out of the way so that a bigger pot gets played against the weakest, most passive range at the table. In a loose live game it is the single most profitable button you can press.

How it plays out

$1/$2, six-handed. UTG limps for $2, everyone folds to you on the BTN with A♥J♠. That limper's range is wide and capped: suited junk, small pairs, weak aces, hands like K♦T♣. It almost never holds AA or KK, because those raise.

You make it $12. Both blinds fold, the limper calls, and you take a $27 pot heads-up, in position, with the stronger range and the initiative. Now compare calling the $2 instead. The blinds come along cheaply, four players see the flop, and A♥J♠ turns into a hand that makes top pair and has no idea where it stands.

Two separate edges paid for the raise: fold equity against the three players still to act, and a heads-up pot against a range yours dominates.

Sizing it properly

Your standard 2.5bb open is far too small here. The limper has already committed a big blind and will call almost anything, so the raise has to be big enough to make the blinds fold and to punish the call.

Situation	Raise to
One limper, you are in position	5bb
One limper, you are out of position	6bb
Two limpers, you are in position	7bb
Limpers plus a caller behind them	8bb or more

Start from your normal open size, add one big blind for every limper, and add one more if you will play the hand out of position.

Which hands to iso-raise

Pick hands that dominate a limping range and still flop something: broadways like AQo and KJs, every pair from 66 up, and suited aces such as A♠5♠. On the BTN you can add suited connectors like 87s, because position lets you realise that equity.

Fold the hands that merely look like a raise. K♦4♦ or Q♦8♦ from the SB against two limpers is dominated by the calls you get and out of position for three streets — a leak dressed up as aggression.

The solver-built preflop charts give you the raise-first-in baseline for every seat. Your iso range sits close to it: a little wider on the CO and BTN, where dead money and position do the work, and clearly tighter from the blinds.