There are a lot more short stackers in today’s games, and ones that are slightly more competent then they were in the past. We’ll define a short stack as anyone with a stack between 15––35 BBs. On most online poker sites the minimum buy-in is 20––30BBs, so most short stackers will be around this range. One of the most important things when facing a short stacker is knowing what kind of short stacker they are, because your calling ranges are going to vary depending on this.
The “leaking my stack” short stacker: This guy is slowing losing his stack and not playing well. Their shoving ranges are not going to be optimal on average, so your calling range needs to widen and adjust accordingly.
The “just lost a big pot” short stacker: If he looks to be aggressive at all, he can easily be tilting, so your range really needs to widen if their stack is 25 BBs or less.
The “buy-in short” bad player: This guy is looking to keep it conservative, but likely doesn’t know exactly what he’s doing. If you haven’t seen him do anything yet, then assume he’s conservative and will have tight shoving ranges of: 77+,AQo+,AQs+. If he’s limped into some pots, or called some pots and been at all active, then he’s likely bad and you can assume a somewhat wider shoving range.
The “pro” short stacker: You’ll have your hands full as this person is looking to play some fun break-even poker. Depending on your stakes, and if he’s good at all, he might make some money. You’ll have to keep somewhat tight calling ranges against him though.
If you are playing a competent short stacker, a general rule is that if you call about 45–48% of your opening range against a shove of 20 BBs, then you’ll generally squeak out a small profit. So for example, if you open 20.4% of your range from late middle position, and a 20 BB short stacker shoves on you from the cut-off, then you should be calling 9%–10.5% of your opening range. That would look something like this: You open: 22+, A3s+, A9o+, KTs+, KTo+, QTs+, JTs, QJo, T9s, JTo. Your calling range would roughly be: 66+, A9s+, KJs+, AJo+.
This is assuming of course they are competent and they aren’t just shoving big hands like 99+, AQs+, AQo+. In that case you’re just going to call with an almost similar range with a few more hands added like AJs, KQs, 88. The bottom line is you want to keep your calling range slightly under 50% of your opening range, unless they are just shoving big hands only and not adjusting to your opening ranges by position.