Quick and Dirty Poker Math

One of the great things about poker math is that you don't have to be right, you just have to be close.

Let me explain.

With so much unknown information involved in every calculation, it's nearly impossible to be 100 percent accurate when deciding your best course of action. That means you can fudge the numbers a bit in favor of ease of calculation. That ease is especially useful when you're in an intense tournament situation or a big money cash game -- it can be hard to concentrate on complex calculations with so much going on.

Here are some quick and dirty tricks to make the math easier in key spots.

Bet X Players

It's always good to know how much the pot is on the flop. Either you're going to want to know how much is a good et for you to make, or what kind of odds a bettor is offering you. The easy way to do this is to simply remember how much the preflop bet was and multiply it by the number of players. And if you don't know how many players are in the pot, the dealer announces it before he deals the flop. I use this announcement to remind myself to calculate the pot right then so I know what to bet and can concentrate on watching my opponents watch the flop come out.

The Rule of Four

The Rule of Four is probably the most popular and most useful of the poker math tricks. On the flop, if you want to know your odds of making a hand, multiply your outs by four. The result will be the rough percentage of times the hand will come in.

For instance, with a four-card flush on the flop, you have nine outs. Nine times four gives us 36%, which is roughly how often your flush will hit if you get to all the way to the river.

Of course, it feels like far less, but that's a subject for a different article.

The Rule of Two

The Rule of Two is the Rule of Four on the turn.

Now that you only have one card to come, you only multiply your outs by two to get your percentage.

Hint: In No-Limit, you're rarely getting the right odds to keep drawing on the turn.

Percentage Conversion

Now that we've got all these percentages, it'd be nice to turn them into odds, wouldn't it? Odds are so much easier to look at when dealing with pot odds to see if you're getting an overlay. 3-1 pot odds and 33% to win could be confusing; state the same thing as 3-1 pot odds and 2-1 against to win and it's clear you're getting an overlay.

To convert percentages to odds, you subtract your number from 100 and divide the result by your number. Your odds are that result to one. In the above example, 100 minus 33 is 67. 67 divided by  33 is 2. I rounded down -- remember we don't have to be exact! So the odds of hitting a 33 percenter is 2 to 1 against.

That's kind of quick, but not real dirty. For the dirty percentage conversion, I just remember 33, 25, and 20. Those are the percentages for 2 to 1, 3 to 1, and 4 to 1 respectively. Anything in between I just estimate.

So in my nine out example in the rule of four, I discover I am a 36% dog. Since 36 is just a little more than 33, I know I am a bit better than 2 to 1 to win.

The actual odds of turning a four-flush on the flop into a flush on the river? 1.8 to 1 against.

Close enough.