Maths is an important part of poker and you need to know your approximate odds at any time in a hand to make the most of your chances of winning.
There will be many times when playing Hold'Em Poker that you'll need a certain card to come out on the flop, the turn or the river. So it is obviously a great benefit to know what the odds are of making you straight or flush on the river.
This sounds difficult but it's not as complicated as you might think. You really need to know two things:
The number of unseen cards
How many "out" cards you have
"Out" cards are the number of cards that can make your hand. For example if you're chasing a flush on the river there are 9 cards that can help you. As there are only 13 hearts in a pack and 4 of them will be out on the board and in your hand, there can be only 9 hearts remaining. The cards held by other players do not count as they ar unknown and therefore does not change the calculation
The other requirement you need to know is the number of unseen cards that there are. As there are already 2 cards in you hand, and before the river there are another 4 cards on the board, there are 46 cards remaining out of the 52 card deck.
Once you master the above information it becomes a matter of a simple sum to calculate your odds. If 9 is the number of cards that can be drawn to achieve your hand, and the total number out there is 46, you divide 9 by 46. (9/46 x 100 = 19.56%).
If quick maths skills are not your forte then try to remember a few before the game:
Flush - if you are holding a four flush, the odds of getting it on the turn are roughly 19% and 19% on the river. The chance of getting it on either the turn or the river is 35%
Open-Ended Straight - the odds of hitting it on the turn is 17% and on the river is 17%. The chance of getting it on either the turn or the river is 31%.
Gutshot Straight - the chances of hitting your card is 8% on the turn and 8% on the river. The chance of getting it on either the turn or the river is 16%
Trips - the odds of turning a pair into three of a kind on the turn is 4% and on the river is 4%. Getting it on either the turn or the river is 8%. Its more likely that you would like to know the odds to catch pocket pairs on the flop and the odds of that is 12%.
If you can't remember the above odds, there is a simple rule that gives the approximate percentage on both the turn and the river. Its called the 4,2 rule.
The numbers relate to the odds on both the turn and the river. To calculate the odds on hitting a card on the turn or the river you need to times the number of outs you have by 4. To calculate the odds of hitting a card on the river you need to times the number of outs you have by 2.
If we look at the previous calculations we can see that this gives a rough guide to the chances of hitting the card that you need. Lets have a look at the flush example, you have 9 outs to hit. Therefore you chance of hitting this on the turn or river is 4 x 9 which is 36%. If it then does not come on the turn the chance of hitting it on the river is 2 x 9 which is 18%.
Another question that always pops up during poker "should I stay in the hand or fold?". Using pot odds you can calculate the odds and make the right decision during every hand.
Pot odds are the ratio between what there is currently in the pot and the amount that you have to bet in order to stay in the hand you are playing. As an example: if there is Â£30 in the pot and you have to bet Â£6 then your pot odds are 5-1 (30 to 6).
If your hand isn't the best at the table at that time but you could be onto a winner if the right card comes out next. There are 4 cards on the table and lets say you hold 4 diamonds. Your odds of getting a flush on the river are about 5:1 against you. That means for you to bet with pot odds there needs to be at least five times your bet amount in the pot already. So if you bet £3 there should already be at least £13 in the pot to make it worth your while.