THE RULE OF 2 AND 4: Now that we understand how to determine our number of outs, we can further explore ‘the rule of 2 and 4.’ In the case of our flush draw, we have 9 outs.
‘The rule of 2 and 4’ works like this:
With the turn and river still to come, we have 2 chances to hit one of our 9 outs. It is just under 20% in terms of our chance to hit our flush with one attempt (river only); and with two attempts (turn & river) our odds increase to about 35%. Here is the ‘rule of 2 and 4‘ calculation: With nine outs, on the turn we take our outs and multiply by 4 (4 x 9 = 36, or approximately 36%). That is a close estimation of the actual 35% odds of hitting our flush with the turn and river to come. With only the river to come, we multiply by 2 (9 x 2= 18, or approximately 18%). Those are both very close approximations of the actual probability figures. This is a quick-and-easy way to estimate our odds and decide if it is worth paying to see the cards that are yet to come on the ‘turn‘ and ‘river‘.
The remaining factor in the decision making process worthy of consideration is, ‘How much money is in the pot?’ Why is this important you ask? It is important because if you do not have reasonable ‘pot odds‘, you should not call the bet. ‘Pot odds‘ are further explained under separate title in the FAQ’s.