Sports Betting Odds Explained: A Beginner’s Guide

Joel Frank
Last updated: | 9 min read

Sports betting commercials are everywhere: NFL games, tennis matches, and even non-sports television programs. You may have seen screens full of numbers representing the odds of one player or team winning the match. When you don’t understand the underlying principles, sports odds can seem like a complicated math problem or a foreign language.

You’re in luck if you hope to learn how to read betting odds. In this guide, beginning players will find betting odds explained, while more experienced players can refresh their knowledge.

Main Types of Odds

At their foundation, odds show the chances of an event occurring. In the case of sports betting, they show the oddsmaker’s opinion on how likely a particular event is to occur.

There are three main types of odds: fractional (British), decimal (European), and moneyline (American). These are simply alternate ways of presenting the same odds; the format makes no difference in terms of winning.

British or Fractional Odds

Also known as British odds, UK odds, or traditional odds, fractional odds are popular with bookmakers in the United Kingdom and Ireland. If you’re looking for an explanation of fractional betting odds, you’ll be happy to know that this formula is quite simple. Fractional odds consist of two numbers separated by a dash, slash, or colon.

For example, odds of 2-1 (or 2:1 or 2/1) mean that you stand to win $2 for every $1 wagered. In this instance, you would receive your profit ($2) in addition to getting back your stake ($1), for a total of $3. Therefore, a winning $100 wager at 2-1 odds will return a total of $300 ($200 in winnings and the $100 stake).

The fractional odds calculation looks like this: Tp = ( S ( N / D ) ) + S

  • Tp = Total payout
  • S = Stake
  • N/D = Numerator/denominator of the fraction (e.g., 2/1)

In our example above, $300 = ($100 (2/1)) + $100.

European or Decimal Odds

The rest of Europe (outside of the UK) tends to prefer decimal odds, as do Australia, New Zealand, and Canada. Also known as European odds, digital odds, or continental odds, decimal odds use a number with a decimal to represent the total amount you get back for every dollar wagered.

Unlike fractional odds, decimal odds include your initial stake in the calculation. For example, odds of 3.00 mean that you win $2 for every $1 you wager, plus your $1 stake. In this case, a winning $100 wager at 3.00 odds will return a total of $300: $200 in winnings and the $100 stake.

The decimal odds calculation looks like this:

Tp = S * D

  • Tp = Total payout
  • S = Stake
  • N/D = Numerator/denominator of the fraction (e.g., 2/1)

In our example above, $300 = $100 * 3.00.

American or Moneyline Odds

If you’re looking for football betting odds explained, you need to understand moneyline odds. Sometimes called American odds or US odds, moneyline odds are most popular in the United States (and with that said, you might want to check out our page California sports betting apps and try moneyline odds now). This version may seem more complicated when you’re first learning how to read odds in sports. A key factor to understand is that American odds revolve around units of $100.

Odds for favored teams have a minus (-) sign to represent the amount that bettors need to wager to win $100. Odds for underdogs, on the other hand, have a plus (+) sign to indicate the amount bettors stand to win for every $100 wagered. You may see American odds for an NFL game expressed as follows:

  • Chiefs: -500
  • Patriots: +375

This means the Chiefs are the heavy favorites in this matchup. American odds contain an implied probability of winning, which follows these formulas:

  • For favorites: Odds / (Odds -100) = Implied Probability
  • For underdogs: Odds / (Odds +100) * 100 = Implied Probability

For the Chiefs, the chance of winning is as follows: -500 / (-500 -100) = -500 / -600 = 83.3%. For the Patriots, the implied probability goes like this: 100 / ( + 375 + 100) = 100 / 475 = 21.1%.

These odds mean that if you stake $100 on the expected outcome (for the Chiefs to win), you stand to get an approximately $120 payout ($19.99 profit, plus your original $100 stake). To make a $100 profit ($99.99, to be exact), you would need to stake $500.

On the other hand, if you successfully wager $100 on the underdog Patriots, you would earn back your initial stake plus a $375 profit (for a total payout of $475).

How To Read and Interpret Odds

Now that you’ve had basic types of betting odds explained, you should have a good sense of how to read and interpret odds in varying formats. Two key factors to keep in mind are as follows: 1) How much do I stand to win per amount wagered? and 2) Is my initial stake included in the odds?

With fractional odds, the number on the left indicates how much you stand to win if you stake the amount represented by the number on the left. For example, with 4/1 odds, you stand to win $4 for every $1 wagered. This does not include your stake, bringing your total payout to $5.

With decimal odds, your stake is part of the calculation. Decimal odds of 4.5 indicate a profit of $3.50 for each $1 wagered, plus the initial $1.00 stake. If you wager $100 on 4.5 odds, you stand to receive a payout of $450: $350 in profit, plus your original $100 stake.

With American odds, your stake is not part of the calculation, so you must add it separately. A minus indicates a favorite, while a plus indicates an underdog. If you see odds of -400, you would have to wager $400 to win $100 (plus your $100 stake). If you see odds of +400, you would have to wager $100 to win $400 profit (plus your $100 stake).

Factors Influencing Sports Betting Odds

A wide range of factors  sports-related and otherwise — affects whether a team or athlete wins a game. Similarly, multiple factors go into determining sportsbook odds, including the following:

  • Sports statistics (win/loss percentage, earned run average, head-to-head match record, home-field advantage)
  • Recent performance (are they improving or on a downward spiral?)
  • Difficulty of schedule (number of games, travel distance, playoffs vs. regular season)
  • Any injuries or suspensions that may affect performance
  • Weather conditions (snow, rain, high heat) that may affect the game

Odds Conversion

Many online tools can help you quickly convert one odds format to another. Many sports betting websites will also allow you to see the odds in your preferred format. If you’d like to convert the odds yourself or understand how the sites calculate them, the following may help.

Fractional to Decimal

  • Step 1: Convert the fraction into a decimal.
  • Step 2: Add 1.
  • Example: Odds of 3/1 = 3 + 1 = 4

Decimal to Fractional

  • Step 1: Subtract 1.
  • Step 2: Convert the decimal into a fraction.
  • Example: Odds of 4 = 4 – 1 = 3 = 3/1

Fractional to American

  • Step 1: Convert the fraction into a decimal.
  • Step 2: If the number is greater or equal to one, multiply it by 100. If it is less than one, divide it into -100.
  • Example 1: Odds of 3/1 = 3 * 100 = 300
  • Example 2: Odds of 1/2 = -100 / .5 = -200

American to Fractional

  • Step 1: If the odds are greater than 0, divide the odds by 100. If the odds are less than 0, then divide -100 by the odds.
  • Step 2: Convert into a fraction, if needed.
  • Example 1: Odds of +200 = +200/100 = 2 = 2/1
  • Example 2: Odds of -200 = -100/-200 = 1/2

American to Decimal

  • Step 1: If the odds are greater than 0, divide the odds by 100. If the odds are less than 0, then divide -100 by the odds.
  • Step 2: Convert into a fraction.
  • Step 3: Add 1.
  • Example 1: Odds of +200 = +200/100 = 2 + 1 = 3
  • Example 2: Odds of -200 = -100/-200 = 1/2 + 1 = 1.5

Decimal to American

  • Step 1: If the decimal is greater than or equal to 2, multiply the decimal minus one by 100. If the decimal is less than 2, divide -100 by the decimal minus one by 1.
  • Example 1: Odds of 3.0 = (3 -1) * 100 = 200
  • Example 2: Odds of 1.5 = -100 / (1.5 – 1) = -200

Understanding the Bookmaker’s Margin

Whether you win or lose, the house always wins. That’s because bookmakers factor their profit margins into the odds. This is why you will see implied probabilities that add up to more than 100%.

In our NFL example above, the probabilities were 83.3% for the Chiefs and 21.1% for the Patriots, for a total of 104.4%. That extra 4.4% represents the bookmaker’s expected profit, a concept known as over-round.

Other Odds Terms You Need To Know

As you start understanding odds, you may also come across the following gambling terminology and concepts.

  • What Are 7 to 2 Odds?

Odds represented as 7 to 2 are fractional odds, which you could also write as 7/2, 7:2, or 7/2. This means you stand to win $7 for each $2 you stake.

  • What Do Odds of +200 Mean?

If you see odds with a plus or minus sign, you are looking at American odds. Odds of +200 mean that a team is a significant underdog, with an implied probability of winning of only 33.33%.

  • Negative Odds

In contrast to the above example, negative odds represent the team favored to win. If you see American odds with -300, for example, you would need to wager $300 for every $100 you stand to win.

  • Las Vegas Odds

If you see the term “Vegas Odds” on a sportsbook, it typically refers to odds (in American format) and lines (moneylines, point spreads, and totals).

Common Mistakes and How To Avoid Them

When planning your betting strategy, make sure to avoid the following odds-related pitfalls:

  • Looking only for big payouts: While you can earn big by wagering on an underdog, you can also lose big. High odds mean more risk, so expect to lose more money if you play this way.
  • Confusing odds and value: Sometimes, the odds don’t reflect the true probability that a team will win or lose. Value bets occur when bettors believe the likelihood of a particular outcome is higher than the odds suggest.
  • Considering only the odds: Although understanding the odds is essential, it’s not the only factor. Good betting practices also incorporate your knowledge about a sport and personal assessment of particular games.

Final Thoughts on Sports Betting Odds

Now that we’ve gone over how sports betting odds work, you can feel more sure about grasping the chances of winning and figuring out the potential profit that you stand to make. Understanding sports betting odds, how they work, and the different ways that they can be presented will give you a better sense of what to expect when placing a bet and boost your confidence in making informed decisions the next time you’re placing a bet at a sportsbook. However, if you are completely new to sports betting, read our guide on how to bet on sports.

Sports Betting Odds FAQ

What does +/- mean in betting odds?

In sports betting odds, a minus sign (-) indicates a favorite, while a plus sign (+) indicates an underdog.

What does a +7 spread mean?

A +7 spread refers to the expected final difference between two teams. For bettors to profit by wagering on an underdog, that team must win a game outright or lose by fewer than seven points.

Want one more type of betting odds explained? If a team loses by exactly seven points, it’s called a “push,” and sportsbooks will refund wager money.

What does 20 to 1 mean?

Odds of 20 to 1 indicate a significant underdog. A winning $100 wager on that team returns 20 times that amount in profit: $2,000 (plus your $100 stake).