How to win at gambling: what are the odds?

Game odds: How do casinos work?

Casino gaming revolves entirely around odds. Betting odds tell players:

• how likely a specific event is to happen within a game
• how much player will win if that event occurs

This likelihood (known as the 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.

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.

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”).

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:

52

Cards in a deck

–

2

Cards in your hand

–

4

Community cards dealt thus far

=

46

46

–

9 ♠

=

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%).

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)

House Edge

2.70%

(1/37)

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 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:

31%

38%

46%

54%

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

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:

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:

Slots odds

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.