Casino games: what are the odds?

If you want to gamble successfully, you need to know about game odds and edges. Each game is unique in this regard. It's up to you to figure out how to minimize the house edge and put yourself at the best advantage. With just a basic understanding of probability, you can make appropriate wagers for whatever scenario. Trust us, you don’t need to be a mathematician to gain enough understanding for the odds to work in your favor.

Online Gambling Game Odds

How do casino game odds work?

Betting odds tell you how likely a specific event is to happen within a game, and how much you will win if that event occurs. This likelihood (aka probability) is usually written one of two ways:

Fractional Odds

These types of odds are written as 10/1, 5/2, etc. and with them you can easily calculate how much you stand to win: if you bet the second number, you win the first number. So, in the first example, if you bet $1 you would win $10.

Odds Fractional Table

If at 5/2 odds you bet $4, you would also win $10 (for every value of the second number you bet, you win the first number plus the return of your stake).

Percentages

Those same fractional odds can be converted to a percentage with a simple formula: Probability (%) = B / (A+B), where A and B are the first and second numbers in the fractional odds, respectively.

Odds Percentages Table

So plugging in the 9/1 example, the completed formula would then look like 1 / (10 + 1) = 0.09, meaning there is a 9% chance that the event will happen.

It’s more common in sportsbooks/betting odds than on casino games, but occasionally you will see odds written as decimals, too (as in 9.0).

Beyond that, every casino game’s odds are a little different.

Texas hold 'em odds

If you’ve ever watched poker on TV, then you’ve seen graphics that display a player's chance of winning a hand based on what they are holding and what is out on the table. This percentage is based off the number of cards remaining in the deck that will help you improve your hand (also called “outs”).

Odds Poker Table

If, say, you are holding Q♠ and 9♠ and on the board is J♠ 2♠ 7♦ A♦, you would calculate your chance of winning the hand by:

Taking the number of cards in any suit (13), then subtracting the number of spades on the table and in your hand (4):

13

4

=

9

This means you have nine outs. To then calculate your approximate odds of completing your flush from this, you would do:

Cards in the deck

52

Cards in a deck

Cards in your hand

2

Cards in your hand

Community Cards

4

Community cards dealt thus far

=

46

Poker cards remaining in deck

46

Spades cards remaining in deck

9 ♠

=
Losing poker cards remaining in deck

37

=

ODDS: 4/1

FRACTIONAL

ODDS: 20%

PERCENTAGE

Of that 46, there are 9 cards remaining that could complete your flush and give you a win. Thirty-seven cards remain that will cause you to lose if any of them are the last card to come out. This makes your odds of getting the win 37:9, which simplified down is around 4:1 (or 20%).

How to quickly calculate poker odds

  • Calculate the number of outs left in the deck after the flop.
  • Multiply this number of outs by 4 – this tells you the chance of getting a winning card on the turn or river.
  • Multiply the number of outs by 2 after the turn – this tells you the chance of winning on the river.

Roulette odds

There are two main versions of roulette, American and European, and both have their own particular set of odds. The house edge (the edge that a casino has over a player) on almost all bets is 5.26% (2/38) in American roulette and 2.70% (1/37) in European roulette. This percentage is calculated by dividing the amount of zeroes on the wheel by the total number of slots.

House Edge

5.26%

(2/38)

American Roulette Wheel

House Edge

2.70%

(1/37)

European Roulette Wheel

From here, we know that the odds on an even money bet (such as red/black, odd/even) are 47.37% (18/38) on an American wheel and 48.6% on a European wheel.

Bets on an individual number give you much lower odds of winning, as does betting on anything else besides red, black, odd, even, 1-18, and 19-36:

Roulette Table

Roulette odds and payouts

BETS
PAYOUT (AMER.)
PROBABILITY (AMER.)
PAYOUT (EURO)
PROBABILITY (EURO)
1:12
2:1
31.58%
2:1
32.4%
13-24
2:1
31.58%
2:1
32.4%
25-36
2:1
31.58%
2:1
32.4%
Single number
35:1
2.63%
35:1
2.7%
2 number combo
17:1
5.26%
17:1
5.4%
3 number combo
11:1
7.89%
11:1
8.1%
4 number combo
8:1
10.53%
8:1
10.8%
6 number combo
5:1
15.79%
5:1
16.2%
Combo of
6:1
13.16%
n/a
n/a

Blackjack odds

Blackjack is commonly regarded as the casino game with the best odds for you to win. However, this claim assumes you know blackjack basic strategy and don’t deviate from it. When you do that on a multi-horse shoe, your odds look like:

Odds you’ll bust

Blackjack Hand 10 2 Off Suit
31%
Blackjack Hand 10 3 Off Suit
38%
Blackjack Hand Jack 4 Off Suit
46%
Blackjack Hand Queen 5 Off Suit
54%
Blackjack Hand King 6 Off Suit
62%

As you’d imagine, your odds obviously continue to decrease as your hand increases in value. Know that there are countless varieties and rule sets for blackjack, for which the odds and your strategy will all vary slightly.

Craps odds

Online Craps Dice

With so many different bets that can be made, craps is perhaps the hardest game to understand your odds with. Before tackling all the different bet possibilities, you should first understand your odds simply of rolling different numbered combinations:

Craps odds and combinations

Dice Total
Possible Combinations
Odds
Odds %
2
1-1
35:1
2.78%
3
1-2   2-1
17:1
5.56%
4
1-3   3-1   2-2
11:1
8.83%
5
1-4   4-1   3-2   2-3
8:1
11.11%
6
1-5   5-1   4-2   2-4   3-3
31:5
13.89%
7
1-6   6-1   2-5   5-2   3-4   4-3
5:1
16.67%
8
2-6   6-2   3-5   5-3   4-4
31:5
13.89%
9
3-6   6-3   4-5   5-4
8:1
11.11%
10
4-6   6-4   5-5
11:1
8.83%
11
5-6   6-5
17:1
5.56%
12
6-6
35:1
2.78%

As you play more and more craps, you (or someone at your table) will occasionally go on a seemingly unbeatable streak. However you’ve probably never seen a streak as hot as the at the Las Vegas Desert Inn in 1950. Reports say an anonymous gambler made 27 straight passes (wins), a feat that has odds against of 12,467,890 to 1. Although his bets were more modest in size, had he bet the house limit on each roll he would have racked up $268 million.

Once you have a feel for the game and its language, reference this chart of the five best and five worst craps bets you can make:

Craps: the 5 best and 5 worst bets

Bet
True Odds
Odds Paid
House Edge
Pass Odds / Come Odds
Same as paid
2:1 on 4,10;
3:2 on 5,9;
6:5 on 6,8
0%
Don’t Pass Odds / Dont Come Odds
Same as paid
1:2 against 4,10;
2:3 against 5,9;
5:6 against 6,8
0%
Don’t Pass / Don’t Come (Bar-12 or Bar-2)
976:949
1:1
1.36%
Pass / Come
251:244
1:1
1.41%
Place 6 / Place 8
6:5
7:6
1.52%
Horn(the combined bet)
5:1
27:4 on 2,12;
3:1 on 3,11
12.5%
Whirl/World(the combined bet)
2:1
26:5 on 2,12;
11:5 on 3,11;
0:1 (push) on 7
13.33%
2
35:1
30:1
13.89%
12
35:1
30:1
13.89%
Any 7
5:1
4:1
16.67%

Slots odds

Online Slots 777

Slot results are determined by a random number generator (RNG) the moment you press Spin. Contrary to popular belief, there is no set order of “payoff cycles” that a machine rotates through. Every spin is independent from the last. Slots have one of the highest house edges in the casino (typically over 7%).

Bear in mind that laws are different everywhere regarding house edge. In Vegas, for instance, the return to player (RTP) can legally be as low as 73% (a house edge of 27%). While there are some headline-making winners out there, big wins are in fact quite rare. The winner of the largest slot prize ever ($39,710,826.36) had to beat odds of 16 million to one. You can read more on our how to wins slots guide.

How to calculate house edge

On online slots, you can typically find out a game’s theoretical return to player (RTP) on either the paytable menu or the rules screen. This will typically be written as a percentage such as 93.00%.

Subtract the RTP as a number from 100 to find the house edge. It would be 7% in this case (100 - 93 = 7).

What this means is for every $10 wagered, players earn $9.30 of it back.

  • This does not mean that every game returns this percentage.
  • Wins and losses happen completely at random in slots.
  • Your return will range between zero and the maximum prize, each time you play.

Remember: casinos have the edge

Only when you understand how the odds work in casino games can you hope to make money playing long term. Sometimes the most important part of understanding the odds is simply learning when's best to walk away. Always consider this option, especially if you happen to win a lot quickly.

Remember, casinos always hold the edge. They wouldn’t stay in business if the odds weren’t in their favor.

For getting to grips with odds in action, you can check out Casino.org's free games right here. With free games, you're not risking any real money.