The Rule of 4 and 2 in Poker

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A man in action at a poker table, tossing playing cards down, with casino chips neatly arranged in front of him.
BetMGM Apr 18, 2024, 3:12 AM

There are many quick poker rules of thumb that you can easily incorporate into your game. Whether you’re playing online poker or in a brick-and-mortar establishment, these handy heuristics can really help newcomers improve quickly.

One of the best-known poker tips is the rule of 4 and 2. It’s a simple way to make poker math a little more manageable. After all, not everyone is adept at performing mental arithmetic, especially when under pressure. If that sounds like you, this article is just what you need.

Relevance of the Rule

Draws are extremely common in poker and, when used effectively, they can be rewarding. However, you’re certain to lose money in the long run if you chase every single straight, flush, and set.

In any long-term successful poker strategy, pot odds are a vital element. To stay profitable, you should only draw when the math says it’s right to do so. But trying to calculate poker odds on the fly in the middle of the hand can be daunting. And that’s where this rule comes in handy.

Rule of 2 Explained

If you’re on the flop awaiting the turn, or you’re on the turn awaiting the river, apply the rule of 2. This allows you to quickly calculate the approximate percentage chance of making your draw.

For example, imagine you’re holding ace-queen suited (clubs) on a board of king, 6, deuce with two clubs. Here, you have a flush draw, meaning the following statements are true:

  • With 13 cards in every suit and four of them visible, only nine are left.
  • There are 52 cards in the deck, and you can see five, meaning 47 remain.

The actual chance of hitting your flush on the next card is calculated like this.

(9 / 47) × 100 = 19.15%. (That’s moneyline odds of +422.)

The rule of 2 calculation is 9×2 = 18%. (Moneyline odds of +456.)

As you can see, there’s a marginal difference in the end results. But the purpose of these rules is not laser-focused precision. Instead, you just need a very quick way to inform your decision when under pressure. This is close enough, with no need to get a calculator out.

Rule of 4 Explained

Now consider the second part of this handy rule. Imagine you’re on the flop, and you’re considering an all-in. This means you’re guaranteed to see both the turn and the river. In this case, simply multiply your total number of outs by four.

For instance, imagine a hand of jack-10 offsuit on a queen, 9, 4 flop. It’s a rainbow board, meaning no threat of a flush. A pair of jacks or 10s isn’t likely to be much use as you’re probably facing at least ace-queen. Basically, you’re only drawing to the straight. 

Here are the facts:

  • Any king or 8 completes your straight, so you have exactly eight outs.
  • You know five of the 52 cards in the deck, meaning 47 remain unseen.

The rule of 4 calculation suggests a chance of 8×4 = 32% (moneyline odds of +213.) But the actual math on this one is slightly more complicated.

Eight of the 47 remaining cards do not make your straight on the turn, so 39/47 do. Subtract one from both of these values, to allow for the river card, leaving 38/46. To find the probability of making the straight, multiply these two values together and subtract from 1.

(39/47) × (38/46) = 0.6854764107308048.

(1 – 0.6854764107308048) × 100 = 31.45%. (Moneyline odds of +218.)

Once again, this is exceptionally close to the approximation of 32%.

Accuracy

The below tables further illustrate just how accurate each of these rules is, starting with the rule of 2. Figures are rounded to one decimal place for ease of viewing.

Draw Outs Rule 2 Chance Real Chance Difference
Flush 9 18% 19.6% -0.7%
Open-Ended 8 16% 17.4% -1.4%
Straight + Flush 15 30% 32.6% -2.6%
Gutshot 4 8% 8.7% -0.7%

And this is how the rule of 4 stacks up.

Draw Outs Rule 4 Chance Real Chance Difference
Flush 9 36% 35.0% +1%
Open-Ended 8 32% 31.5% +0.5%
Straight + Flush 15 60% 54.1% +5.9%
Gutshot 4 16% 16.5% -0.5%

How To Calculate Pot Odds

You can see that these simple rules are extremely accurate. But what exactly do you do with this information? 

The idea is to calculate the odds currently offered by the pot, also as a percentage, and compare the two figures. If the value offered by the pot is equal to or greater than your actual probability of hitting, it’s correct to continue. If not, you’d be making a losing play.

To work out your pot odds as a percentage, take the call amount and divide it by the total pot after making the call. Then multiply by 100.

For example, imagine there’s $8 in the pot, and you are facing a $2 bet. If you make the call and win, you’ll pick up a total of $10 for your $2 bet.

(2 / 10) × 100 = 20%. (Moneyline odds of +400.)

Common Errors

Here are some frequent mistakes made by beginners when applying the rule of 4 and 2. Don’t fall into these traps.

Only for Hold’em

The rule of 4 and 2 only applies in Texas Hold’em. Its logic relates to the number of unseen cards left in the deck. Games like Omaha or Short Deck Poker are completely different in their structure, rendering this trick useless.

Incorrect Pot Odds

One of the most common poker mistakes is forgetting to include the call as part of the pot when calculating odds as a percentage. If you forget to do so, your math will be quite inaccurate, leading to poor long-term decisions.

Clean Outs

The idea behind these rules only works if you actually win the pot when completing your draw. If you’re drawing to a small flush that will likely lose to a better one, the theory flies out of the window entirely. 

Other Casino Heuristics

The rule of 4 and 2 is not the only online casino shorthand you’re likely to encounter. Here are a few other top time-saving tips:

  • Poker’s ten-to-one rule: If you ever find yourself in a tournament spot where you have 10x your opponent’s stack, automatically put them all in. 
  • Always split aces and 8s: When playing blackjack, failing to split either of these starting hands is a losing play. Don’t worry about the math — you can take it on trust.
  • Surrender 14, 15, and 16 against a 10: If the blackjack surrender rule is active, automatically give up half the bet to avoid playing these long-term losing hands.

Poker Games 4 You 2 Enjoy at BetMGM

Now that you’re familiar with these handy pot odds rules, you can begin to incorporate them into your own game. Why not register with BetMGM and hit the micro-stakes cash game tables? Here, you can practice making these calculations on the fly with minimal risk.

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Our BetMGM editors and authors are casino experts with a wealth of knowledge of the online casino industry at all levels. Their coverage includes company news, game reviews, how-to instructional articles, strategy guides, and editorials showcasing BetMGM’s superior product and game library.

Our BetMGM editors and authors are casino experts with a wealth of knowledge of the online casino industry at all levels. Their coverage includes company news, game reviews, how-to instructional articles, strategy guides, and editorials showcasing BetMGM’s superior product and game library.