How to Read and Understand American Odds

Anyone who’s ever played a sport knows that you have to start by mastering the basics – the foundation upon which you build your knowledge and skill. Sports betting is no different – and learning how to read and understand American odds is as basic a skill as it gets.

How do odds work in betting?

When placing a bet, the odds tell you how much you have to risk to win however much is on offer. The odds essentially therefore make the bet.

Odds can also be displayed in decimal and fractional formats, but here we’ll focus on American odds – the default format used by all sportsbooks in the US, and offered globally by any online sportsbook.

What do American Odds Mean?

American Odds Identify Favorites and Underdogs

The first thing to learn about American odds, is that in a head-to-head match-up, they immediately identify the favorite and the underdog. This could be a football, basketball, hockey or baseball game, a tennis match, or a fight.

Another basic requirement is knowing what it means when sportsbook identify, and people are talking about, the favorite and the underdog. How does that relate to your betting?

The favorite is the party expected to win; the underdog is the party expected to lose. Click on the links to read more about both.

Examples of American Odds

Let’s take a look at how this all plays out with some real life examples, using this weekend’s NFL Conference Championship games between the Chiefs and the Bengals in the AFC, and the California clash between the Rams and the 49ers in the NFC game.

Below are the moneyline odds as offered by Stake.com at the time of writing. (Basic skill #5: When reading anything about odds on a game, remember to always check live sites for updates).

If we return to our three truths about American odds:

1. The Minus Sign Denotes the Favorite

In American odds, the favorite appears with a minus sign. The size of the number illustrates the extent to which a favorite is favored to win.

In the first match, Kansas City are favored at -286 over Cincinnati at +245.

In the second match, Los Angeles are favored at -179 over San Francisco at +155.

You can tell from the difference between the numbers that the Chiefs are more heavily favored to win over the Bengals than the Rams are over the 49ers. Or to put it another way, the match between the Rams and the 49ers should be closer than the one between the Chiefs and the Bengals.

2. The Plus Sign Denotes the Underdog

Getting used to the phrases and terminology used around sports betting might take you a little while, but it “pays to look at the other side” – which is a common phrase you’ll hear from time to time.

In American odds, the underdog appears with a plus sign. The numeral illustrates the extent to which the underdog is expected to lose.

While this may seem painstakingly obvious to state out loud, it’s never a bad idea to help your understanding along in the early days. Given what we know above, it should be clear that:

In the first match, Cincinnati are underdogs at +245 against Kansas City at -286.

In the second match, San Francisco are underdogs at +155 against LA at -179.

3 . American Odds Always Relate Back to $100

So what do these numbers actually mean for your bet?

For the favorite, the odds show how much you need to bet to win $100.

• If you want to back the Chiefs at -286, you need to bet $286 to win $100.
• If you want to back the Rams at -179, you need to lay $179 to win $100.

For the underdog, the odds show how much a $100 bet would return.

• If you want to back the Bengals at +245, $100 would win you $245.
• If you want to back the 49ers at +155, $100 would win you $155.

Of course, that’s not to say you have to bet $100. The math scales to however much you decide to bet.

If you bet $20 on a favorite at -200, you would win $10, for a total payout of $30. At minus odds, recall that means a $200 wager to win $100.

If you bet $50 on a +400 underdog, you would win $200 for a total payout of $250. At positive odds, that means how you would win $400 on a $100 wager.

American Odds Calculator

Prospective bettors – and indeed seasoned sharp bettors – can use The AllStar’s Betting Calculator to enter their proposed stake and the odds – in any format – to calculate the potential payout they stand to receive.

However, there is always value in understanding the math that underlies these conversions, and it isn’t too complicated.

American Odds to Decimal Odds

In Europe, bookmakers usually display decimal odds. Most online sportsbooks allow players to choose the style of odds display they are most comfortable with – be it American, Decimal or Fractional.

When American odds are positive, the formula to convert these to decimal odds is:

(American odds / 100) + 1 = decimal odds. 

The formula is different when the American odds are negative:

1 - (100 / American odds) = decimal odds.

Decimal Odds to American Odds

If you want to convert decimal odds for a favorite (odds of below 2 and greater than 1) to American odds, the formula is:

-100 / (decimal odds - 1) = American odds

To convert decimal odds on an underdog (odds of 2 or above) the formula is:

(Decimal Odds - 1) * 100 = American odds

In Conclusion

And that’s your introduction to American odds. To recap, here’s what you really need to remember:

• In American odds, the favourite takes a minus number, the underdog takes a positive number.
• The size of those odds reflects the extent to which the bookmaker feels one team is favored, and hence also how much of an underdog one team is seen as being.
• Odds of -200 signify a clear favorite, but odds of -1500 suggest a heavily favored favorite. Similarly, odds of +200 signify a clear underdog, while odds of +1500 suggest a true rank outsider. (What makes sports so intriguing is the knowledge that underdogs do cause massive upsets – and the element of chance that this can happen on any given (Sun)day.)
• When trying to calculate your potential winnings, you can always use a calculator to do the math for you – but on a favorite, American odds show how much you need to lay to win $100, while on an underdog the odds show you how much a $100 bet would win you.

(American odds / 100) + 1 = decimal odds. 

(110 / 100) + 1 = 2.1

1 - (100 / American odds) = decimal odds.

1 - (100 / -130) = 1.769

-100 / (decimal odds - 1) = American odds

-100 / (1.71 - 1) = -140

(Decimal Odds - 1) * 100 = American odds

(2.1 - 1) * 100 = +110