Isolation Raise

Also known as: iso raise, isolate, iso-raise

Raising over one or more limpers to play heads-up in position against a weak, capped range.

An isolation raise (iso) is raising over a limper to thin the field and play heads-up — ideally in position — against a player whose limp caps their range and signals weakness. The goal is to attack a poor opponent's equity realization: they entered passively, will check-fold flops often, and rarely have the strength to fight back correctly.

Iso sizing is larger than a standard open to discourage cold-calls and overlimps — a common formula is the normal open size plus one big blind per limper (e.g. 2.5bb + 1bb per limper). Against a single weak limper on the button you can iso with a linear, value-leaning range: strong broadways, decent aces, pocket pairs, and suited hands that flop well heads-up.

The more limpers and the more players still to act, the tighter you iso — overlimps and squeezes loom, and multiway erodes your equity edge. Position matters enormously: isolating in position is far more profitable than OOP, where you surrender initiative on later streets. Against a strong, balanced limping strategy (rare outside high-level play), wide isolation is a mistake — those players limp to trap.