discounting equity caclulated by the 4/2 rule

The easiest way is just to add or subtract outs as you see fit. It won't give you an exact answer, but it works pretty well on the fly.

For example in your AJ flush draw example, assuming you don't know your opponent's cards, I would more often add outs.

I would think, I have 9 outs to the nuts and sometimes if I catch an ace or jack that might be good too. But depending on how strong the action is you're facing you'll likely want to discount some of those outs.

So if you have 9 outs to the flush and 6 outs to a pair larger than the current top pair, you might discount 3 of those outs and assume you only have 12 outs instead of 15.

Remember you typically don't know your opponent's cards. Sure against exactly a set you will be in worse shape, but it's also possible your opponent could have a worse flush draw, and ace high could win unimproved. The important thing is trying to estimate your equity against their range.

Thanks for taking the time to reply. Firstly, an ace or jack wont help my cause here because the opponent already has a set of 5s - assuming i know my opponents cards. While it's true that i will never know what my opponent has, for this question my assumed range for my opponents cards is 55 or 44. So now what i want to know is - how do i adjust/discount the 36% equity that i got from the 4/2 rule to account for the fact that my opponent has a set already and could get to a full house or quads on the turn or river. The online equity calculators show it is 25% and they probably get to this number using simulations. But how do i get from 36% to 25% if i am sitting at a table?

How do you know you're facing a set when you're sitting at a table facing a bet?

The 4/2 rule is just a way of estimating the odds of your draw hitting based on the number of outs. It's not designed to account for being out drawn, and it's not a comprehensive equity calculation.

If your opponent is drawing to a better hand than you're drawing to you have to subtract out the odds of them making their draw from the odds of you making your draw. You also need to account for any overlapping cards, any circumstances where you can win unimproved, etc.

A simple heuristic is a set will improve to a full house or quads 1/3 of the time with two cards to come so ~1/3 of the time you hit your draw you will still lose. That's not accounting for overlapping cards and is just an estimate, as the 4/2 rule is just an estimate.

Shorthand estimate:

36% - (1/3*36%) = ~ 26%

Rarely a situation you want to be in.

To avoid confusing anyone with my previous post, to correct myself 1/3 of 36 is 12 not 10. So using the heuristic I mentioned 36-12= ~24%.

Not sure what I was thinking when I wrote that 36% minus 1/3 of 36% was 26%.

Thank you, this is very helpful.