This is a discussion on Rule of FourTwo within the online poker forums, in the Learning Poker section; I know that this will generate a great number of replies to defend the Rule of FourTwo.How can you defend a rule that is only 

Rule of FourTwo 
#1




Rule of FourTwo
I know that this will generate a great number of replies to defend the Rule of FourTwo.How can you defend a rule that is only half right, (their odds on the river are at least correct). To put it simply there is no mathematical justification to support this manipulation of statistics. Whoever thought that, say, with a flush draw after the flop, that although the true odds of making a flush are 4/1, because you have two chances of making it, (the turn and the river), your odds on the turn, are halved to 2/1. It seems like a case of knowing the answer and working backward to find an equation to justify the means. They combine both the turn and the river in the sane calculation and treat them as being mutually inclusive, which they are not. They are mutually exclusive. With nine outs after the flop your chances of making a flush are 4.22/1 on the turn and 4.11/1 on the river
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Question about this betting rule  9  February 18th, 2021 8:56 PM  Learning Poker 
#2




I haven't seen anyone ever promote it as anything more than a rough indication of your odds.
But that said, I'm not sure you're actually using it right. The Rule of 4/2 says that on flop you multiply the number of outs you have by 4, and that gives you a rough indication of your odds of catching that card by the river. On the turn, do the same but multiply by 2. So say you've got nine outs to a flush on the flop, 9 x 4 = 36%, actual odds are 34.97% Nine outs to a flush on the turn, 9 x 2 = 18%, actual odds are 19.57% So the error on the turn is actually much bigger than the error on the flop.
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#3




And, if you read Phil Gordon's book he pretty much says it's not exact and is only a rough indication if you need to make a quick decision. Much of the time, this quick calculation will be enough...but not always. How many times do you not want to sit and think too long in fear of how it would look to other players? This lets you keep moving quickly if you don't really need to tank.
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Serenity now! 
#4




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making $$ is easy,,,holding on is KEY. 
#5




While this is not exact, there is no way to know the true odds because you don't know what hands (cards) went in the muck. On a flush draw 4 or 5 hearts could have been mucked. A second problem is that unless you are drawing to an Ace high flush, none of the 9 "outs" are really outs. You could have only 12 outs because your flush is no good. Its never good to get too wrapped up in the exact math percentages because unless its on TV, you will never know what the percentages are. Find good rules of thumb that help you make good long term decisions and work on other aspects of your game.
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#6




re: Poker & Rule of FourTwo
I think the rule of 4 and 2 is an easy way for a beginning player to start to understand and apply math into their poker game. I think it gets you close enough in most cases until you learn to do the math in your head, especially in a tournament.
Let's remember this was a tool to get newer players introduced to the percentages without needing a calculator or a pen and paper at the table.
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#7




The rule of 2 or 4 is used as a quick way to calculate the percentage chance of an out hitting. You can do other methods to get an even closer approximation, but a lot of players find the formula [Outs x 2 + 1] = % to be a lot quicker. It looks like you are misunderstanding the rules of 2 and 4. The rule of 2 is used in situations where you must calculate the % of your out hitting within one card. So, on the floptoturn card, you use x2. On the turntoriver, you use x 2. This is done because there will be situations where you can call on flop, but fold on turn. So, you have to calculate each situations independently. In rare situations where you be GUARANTEED to see the turn and river, you will use the rule of 4. This is in situations where a player is allin and there is no chance of you ever folding your hand to a future bet. Since you are going to see both cards, you can use x4 to see your odds of hitting on both turn or river.
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#8




I think this rough indicator can help a lot of people when they find themselves on a hard spot to play, but i dont think it should be taken to the risk and be used as a rule of thumb. Usually its not always needed to stay thinking much about it, especially on microstakes, cause the players usually tell you what they have or its not hard to guess their range on a specific hand
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#9




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#10




So with 9 outs on flop, it would be: 47(unseen)  9(outs) = 38/9 = 4.22:1
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#11




informative thanks.
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#12




re: Poker & Rule of FourTwo
But I agree, if you can't do that or it's one you haven't memorised or you don't have a printed chart available then the 4/2 rule is near enough for a rough calculation  especially if the pot odds you're being laid are big enough that it doesn't matter if your outs calculation is out by a percentage point or two.
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#13




Has anybody ever questioned why you multiply the outs after the flop by 4 then by 2?. This gives you odds of 1.9/1 and 4.1/1 on the turn and river respectfully. Unfortunately for the players who use this system, the true odds are 4.22/1 and 4.11/1
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#14




It is not x4, then X2. It's either: x2 on flop to turn, x2 on turn to river or x4 on flop for turn and river. It's never x4 then x2 in one hand.
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#15




It's good to get acquainted with what is a bad call based on the math. That's how I use it
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#16




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#17




OK, help me out here, what is the mathematical reason for multiplying your outs by anything; why not multiply by 5 or 6 or 3?. I appreciate that it's a rough guide, but it's still an inaccurate one, well 50% inaccurate.
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#18




re: Poker & Rule of FourTwo
And I still don't understand where you're getting the "50% inaccurate" thing from. We've demonstrated above how the rule is supposed to be used, and how close it is to the actual probabilities. Neither number is out by 50%, nor is it the case that one is pretty close but the other is way off. They're both reasonably close.
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#19




Sorry, but can you give me a breakdown down of the mathematical calculation why 4 and 2 are used shoot me the complete sum. It looks like somebody has arrived at the answer and manipulated the workings to suit the answer. The reason it is 50% accurate is that the odds given for the turn are wrong, half of what they should be, but the odds for the river, surprisingly, are correct.
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#20




OzExorcist. Is it true that there is a new beer being sold in Australia? It's called Dicken Cider. Apparently the women can't get enough of it
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#21




Let's say you have 45s and the flop is 68Ar. You have 4 outs to a gut shot straight. According to multiple odds charts online, you have an 8.5% chance to hit on the turn. Using the rule of x2, 4 x 2 = 8. This is pretty close to 8.5% The odds of hitting on the river, from the turn is 8.7%. Using the rule of x2, you get 8. Still close enough to the actual odds. Now, if your opponent is all in on the flop, you only have to call 1 bet to see the turn and river, which is why you calculate the odds of either street hitting, because you are guaranteed to see both streets. According to the charts, you have a 16.5% of hitting on either street. Using the rule of 4, 4 x 4 = 16. Close enough. So, the reason why you would use the rule of 2 or 4 is because it's an easy way to get really close to actual percentages.
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#22




Originally this thread started out as Rule 4 2 but now you have changed it to 2 4, which is more accurate that the other. You calculate in percentages, while do my sums in odds. 8.5% is 11.76/1 against 10.75/1 true odds for the turn and 10.5/1 for the river. If your opponent goes all in on a $200 pot on the flop, it will cost you $200 to play in a $400 pot. Would you need to know your odds were 6/1 before you fold (unless you had the nuts). Good luck to you if you have faith in these charts.
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#23




In your example, your pot odds are 2:1. Whether you should call or not depends on your hand and the board. Since a player goes all in on the flop, the rule of 4 is used and if you have 9+ outs, it's a profitable call. Not sure what you mean about "having faith in these charts". It's literally just math that someone did and charted. It'll literally be the same answer if you did the math yourself, correctly.
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#24




re: Poker & Rule of FourTwo
For a rule to be valid it must return the some result throughout all of its parameters, or it can declare a percentage error which cannot deviate from the declared percentage. Unfortunately Rule 2 does not fit into this category. It is roughly 0.25% error difference between the chart and the true odds (negligible) at 2 outs, but the margin of error increases proportionally as the number of outs increase, reaching the maximum error at 21 outs. I don't wish to be picky, but since the results returned are not identical, the rule cannot be valid. The chart author didn't think it through thoroughly enough. BTW can anybody tell me how you get an out of 1, thanks
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#25




It's been said a few times that the rule of 2/4 is a guide to quickly get to the exact percentage. It went get you exactly there, but close enough. It's a shortcut. If you want the exact odds, feel free to do all that extra work. 2. Are you seriously nitpicking about 21 outs? Yes, the x4 might be a bit off, I agree. But are you ever folding with 21 outs? Anything that is a 51%+ favorite is pretty much a snap call in most situations. Being a 65%+ favorite requires absolutely no calculations to call. 3. 1 out = 1 card to straight flush vs nut flush. Or you have a boat vs quads and 1 out to improve to better quads.
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#26




Yes, the rule breaks down at especially high values for the turn and river combined. But the vast majority of drawing situations in poker fall between four (gutshot straight) and 10 (set drawing to boat/quads on turn) and as you can see, those values are all in the right ballpark. You'll also notice that the Rule of 2 values all err under the actual values  so if you do your pot odds calculation using the Rule of 2 value and it comes out profitable, you're actually in even better shape than you thought. Getting more accurate results would involve using a more complicate rule or just, y'know, using the actual numbers. If you can do the actual math in your head, good for you. Others may just use the actual numbers on an odds chart until they've got the common ones committed to memory (that's what I did). But for people that can't do one of those things, they can use the Rule of 4/2 and get close enough.
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#27




Call it a guide  not a rule. It cannot be a rule with errors in all the outs calculations, At least the last column look close to the actual, until you start to work out the percentage error. Anyway, I think enough has been said about this topic. Thanks to all
OzExorcist, go to youtube and check out 'Dickens Cider', it's from Oz. you'll love it
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#28




So this whole thing has been over whether it should be called a rule or a guideline?!?!?!?!?!?!? Every explanation of how to use the rule (or guideline if you insist) explains that it's a rough guide. If you know that it's just a rough ballpark answer, not the 100% accurate one, what does it even matter?!? And I couldn't care less about drinks with bawdy puns for names.
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#29




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#30




re: Poker & Rule of FourTwo
Oz/OSMB: It's just a shortcut...whatever, fine. It's the "guide" of 2 and 4. Running Nose: Well, since is a guide and not a rule, I guess 18% and 19.6% is close enough. Yeah, the math all works out now!
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#31




https://www.cardschat.com/forum/lear...42a302941/ so let's try again: 42 is the answer to life the universe and everything.
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Question about this betting rule  9  February 18th, 2021 8:56 PM  Learning Poker 