ISO raising is crucial to maximising winrate in softer poker games and their environments. It allows us to increase the number of pots we play against the weakest preflop limpers at the table.
ISO stands for ‘isolation’.
Therefore, the objective is to isolate ourselves against a weaker limper in a heads-up pot.
ISO Raising – Recommended Sizing
Correct ISO raise sizing can vary heavily, depending on the context – but here is a default recommendation as a starting point.
ISO Raise In Position – 4bb plus an extra 1bb for any additional limpers aside from the original.
ISO Raise Out Of Position – 5bb plus an extra 1bb for any additional limpers aside from the original.
Examples of spots where we might ISO larger:
- We are constantly getting multiple callers (perhaps in the case of a live game).
- We have a value poker hand, and our opponent hardly ever folds preflop.
Examples of spots where we might ISO smaller:
- The effective stacks are shallow
- We have a speculative holding and are mostly ISO raising, so the BB doesn’t get to freeroll a flop by checking.
ISO Raising – Recommended Ranges
Decent ISO raising ranges are similar to RFI (raise-first-in) ranges but usually slightly tighter.
For example, the following charts outline hands from each poker position:
Common Questions About ISO-Raising Ranges
Q: Are these solver ranges?
A: No, these are hand-crafted ranges. Since a competent opponent won’t open limp, solvers don’t generally produce ISO raising ranges.
Q: Could we force a solver to limp and therefore create solver-approved ISO-raising ranges?
A: We could theoretically do this, but a solver assumes that the limper is a perfect GTO poker player, so that the range construction won’t be ideal.
Q: Why does the SB ISO raising strategy have an extra component?
A: This component represents our ability to ‘complete’ by paying the extra half of a big blind. Although the poker term ISO implies raising much tighter when OOP, we should also fold a lot.
We get a great price to see a flop by completing, and can do so with a wide range.
Q: Do I need to follow these ISO-raising ranges exactly?
A: No, these are rough guidelines. We should modify the ranges based on what we know about our opponents.
Q: Do I need to change my ISO raising range if there are multiple limpers?
A: Generally, no. Although we’ll invest more in the ISO raise, there's potentially more dead money to win preflop. Our objective is still to either generate a heads-up pot against a limp-caller or take the pot down preflop.
Q: Does the position of the limper matter?
A: Generally, no. Limping ranges will be roughly the same regardless of position. If our opponent knew enough about the game to use positional limping strategies, they would also know enough to avoid open limping entirely.
Q: Do I need to worry about players behind?
A: Yes, if there are aggressive 3betters behind, we’ll need to make sure our ISO-raising strategy doesn’t get too far out of line.
On the other hand, if there are tight/passive players behind, we may be able to ISO raise even wider.
Q: What about limping behind? Is that an option?
Limping behind, AKA 'over limping', can be a strong option for increasing the number of pots we play against weaker players. If a holding is too weak to ISO but potentially playable, we can consider over limping.
Ever wanted to dig deep regarding overcalling? Check out the next article: How to Take Advantage of Overcalling.
