How are draw odds calculated?
To calculate your draw odds, the calculator generates every possible combination of cards that could be drawn from the deck. For each combination, it evaluates the best 5 card hand that can be made and tallies up how often that a hand is made. This yields the precise probability of making each hand type.
This is a computationally expensive process. For speed and performance benefits, draws odds have been pre-computed and stored. This means that rather than recalculating draw odds every time, the calculator only needs to lookup the correct values from a table; albeit a very large table.
For a guide on how to calculate draw odds manually yourself, see our guide to calculating draw odds and outs.
Why are the draw odds different to what I expected?
Calculating draw odds is tricky. To understand how and why the odds above may not be quite what you expected it is best to use an example.
Let's say that you have AS and KS in your hand and you want to know the odds of making a pair on the flop. There are 6 cards that can make you a pair (3 Aces and 3 Kings).
To calculate your odds you may intuitively say that the odds of drawing an Ace or a King as the first card of the flop is 6 divided by the 50 remaining cards in the deck and you would be correct.
For the second card of the flop you might be inclined to say that it would be 6 divided by the 49 cards remaining in the deck. However, you must also consider what impact the first flop card made on your odds. This is where the math can get tricky.
Let’s say the first flop card is a 7D. If the second flop card is any other 7, even though you have not paired your hole cards, the hand you have made is still a pair; a pair of sevens.
Using the same example of AS, KS, another consideration is what if you make a better hand like 2 pair or 3 of a kind?
If the first of the flop cards is an Ace, great you've made top pair! However, if another Ace or a King comes you have no longer made a pair you have made a better hand.
The Bet Shrew odds calculator factors these consideration in as it determines every possible combinations of cards that could be drawn, evaluates the best 5 card hand that can be made and aggregates the results to determine their probabilities.
For draw odds based on outs, check out our drawing odds and outs table.