I'm sure most of you regular poker players are aware of this easy system,but for those of you who are not here it is....very quick and easy method even though there are more precise ones out there..

The Shortcut ? The Rule of 4 and 2

Now that you have worked through the math and seen the theory, it is time to introduce a handy shortcut that will help you calculate your chances of winning a hand within that short period of time that Internet poker allows you to make a decision.

You still need to calculate the number of outs you have in the deck, but once you know that number, the rest is as easy as going all in pre-flop with a pair of aces.
After the flop, simply multiply your outs by four to give you your percentage chance of getting a card you need on the turn or river. However, once you have seen the turn card you should multiply your outs by two to get your percentage chance of hitting an out on the river.

Therefore, if you have eight outs after the flop, your chance of hitting a card you need is: 8 x 4 = 32%. Once that turn card has been seen, your chance drops to 8 x 2 = 16%.
While this method is not super precise, it provides a clear enough guide when playing online poker. Of course, the purists out there will still want to do mental gymnastics to get the exact percentage figure, but for the rest of us mere poker mortals the rule of 4 and 2 is more than sufficient.