American odds is the way the sportsbooks list or display odds here in the United States. If you’re not an experienced bettor you might not even think twice about how the odds are listed, but only in the United States do sportsbook list odds in this way. There are also decimal odds and fractional odds.

American odds are based on either risking or winning a $100 bet. The favorite (more likely outcome) is always listed with a minus sign, while underdogs (unless very small underdog) are listed with a plus sign.

The minus sign means that the number following it is the amount the bettor needs to wager to win $100. So with our Cardinals/Lions example, if a bettor had bet on the Cardinals to win the game at -800 odds the bet would have needed to be $800 in order to profit $100.

The plus sign shows the amount that a bettor will profit if the bet wins. So the Lions winning listed at a +500 price made a $100 bettor $500.

Remember, if the bet wins the bettor also gets their stake back. So using our examples, a winning Cardinals bet risking $800 to win $100 would have returned $900, and a winning Lions bet for $100 to win $500 returned $600.

Of course, the vast majority of bets aren’t exactly $100 but the math still applies. Someone could have bet $5 on the Lions at +500, won $25, and walked away with $30. On the other hand, there could have been a $50,000 bet on the Cardinals that would win $6,250 and send the bettor home with $56,250 if it had won.

Let’s take a look at two more examples of American odds at +200 and +220. Remember that the plus sign means profit per $100. If the Detroit Lions are underdogs in the game and listed at +200 on the moneyline and you bet $100 you can potentially return $300 for a profit of $200.
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If the Detroit Lions were +220 odds when the lines first dropped and you bet your $100 early your possible return would be $320 for a $220 profit.

If your bankroll is not big enough to be dealing in bet units of $100 simply remove a 0! A $10 bet at +200 odds is going to return $30 or a profit of $20. Similarly, the +220 at $10 will return $32 or a profit of $22.

20 to 1 odds is dealing with fractional odds instead of American odds. Sports are not limited to just the United States and often we’ll hear the media using fractional odds and American odds interchangeably. Luckily, it’s pretty easy to convert 20 to 1 odds into American odds.

Fractions quote the potential profit should the bet succeed relative to the stake. In our 20-to-1 example, every dollar you bet should return $20 plus the $1 you initially bet if it wins. In order to convert this to American Odds all we have to do is divide the fraction and add two zeros.

If the numerator of the fraction is larger than the denominator the bet will be an underdog bet and have a plus (+). If the numerator is smaller than the denominator the bet will have a minus (-).

To show the work on our 20/1 example:

When American odds are part of a spread, you will see the odds (usually in the -105 to -120 range, most often -110) accompanied by a point spread or an over/under total point value. Be sure to pay attention to both the American odds AND the actual point spread or total when placing a bet.

Let's look at an example NFL game - the Patriots vs the Colts

This is showing the American odds for 3 separate bets - the Spread, the Total, and the Moneyline.

Think of the Spread like this - how many points will the favorite win by? In the example above, the Colts are the favorites because they're listed at -2.5 points for -110 odds. That is, you can get -110 odds if you bet on them to win by at least 2.5 points.

On the flip side of this bet, the Patriots are 2.5 underdogs. You can get -110 odds if you bet on them to lose by no more than 2.5 points.

Total is simple - how many points will be scored in the game? You're betting that it will be above or below a set amount. In this case, you're getting if the point total will be over or under 46 points.

This is the simplest bet of all - you're betting on which team will win the game!

All sportsbooks should immediately calculate the odds and payout for you when you enter the amount you want to bet, but if you want to do your own calculations just follow this formula. Again, we’ll use a $100 bet on the Lions as a +500 underdog as an example.

The amount risked multiplied by (moneyline/100), which is $100 * (500/100).

Simplified, $100 * 5 = $500

For favorites like Cardinals -800, do amount risked multiplied by (100/moneyline * -1), which in the example becomes $800 * (100/(-800 *-1)), which equals the $100 the bet would win.

Simplified, $800 * 0.125 = $100

Decimal odds are another popular way odds are listed, especially overseas. If the American odds are positive (underdogs), convert using this formula:

So for Lions +500, the formula is (500/100) + 1, which equals 6.00

For negative odds (favorites), convert using this formula:

For the Cardinals example from above, at -800, the formula becomes 1 – (100 / -800), which equals 1.13.

Another way books display odds is by using fractions, called fractional odds, which is seen most in Horse Racing and futures. Simply multiply fractional odds by your stake to determine your payout. If the bet is positive (Lions +500), the formula is:
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Our Lions +500 example would turn that into 500/100, which can be reduced to 5/1.

If the bet is negative (Cardinals -800), the formula is:

Our example would turn that into -100 / -800, which is reduced to 0.125/1.

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Sometimes it can be easier to convert fractional odds into American Odds instead of Decimal Odds. In order to do that, obviously, you have to be able to convert the decimal into a fraction.

For conversion of decimal odds to fractional, you can use this formula:

In the context of our 1.5 example, it would look like this: