At a glance, sports betting odds can look confusing. With plus and minus signs, decimals, or fractions associated with each team and betting market, it may not be obvious what these numbers actually represent to beginners. 

However, the reality of betting odds is that they’re simply a pricing system used by sportsbooks, telling bettors two key things: 

  • First, they show how likely an outcome is considered to be.
  • Second, they determine the potential winnings associated with different markets if a wager is successful.

Understanding how sports betting odds work is essential before placing wagers. Once you know how to read the numbers, the sportsbook board becomes much easier to interpret. Instead of seeing random figures beside teams, you begin to recognize them as probabilities and payouts combined.

We look at sports betting odds explained in simple terms, covering the three main odds formats used around the world, explain how payouts are calculated, and show how sportsbooks determine prices for different events, including on less popular options such as tennis betting and baseball betting.

The Basic Idea Behind Betting Odds

At their core, betting odds show the relationship between probability and potential payouts for different outcomes. It remains the same across pre match markets, in-play betting options, and across virtual sports betting odds.

When one situation is considered more likely, the returns are lowered, and vice versa for outcomes that are less likely, with their potential payout becoming larger. This is why favorite odds and underdog odds differ:

  • A favorite is the team or player expected to win the event. Due to their chances of winning being higher, sportsbooks offer smaller returns on bets placed on that specific outcome.
  • An underdog is the team or player that is considered less likely to win. Because the probability of them being successful is lower, sportsbooks offer larger payouts to attract wagers with higher odds.

This balance between risk and potential winnings is what shapes the foundation of all sports betting odds.

An example of this would be a football game between two teams, both of which have different chances of winning. Team A might have odds of -180, making them the favorite, while the underdog, Team B, could have odds of +150. 

In this situation:

  • Betting on Team A requires a larger stake to produce a higher potential return.
  • Betting on Team B requires a smaller stake but offers a larger potential return. 

Decoding the Three Main Formats

how do sports betting odds work

Sports betting odds often appear in three different forms, and while they may look different, they all show the same information.

The three most common formats are: 

  • American odds
  • Decimal odds
  • Fractional odds

As usual, all these odds show the probability of a team or player being successful in a match, alongside the potential payouts. The only difference is how they appear, with most bettors having a favored format that they understand or can read faster than the others.

American Odds (The +/- System)

Just like the name suggests, American odds are the most common format used across North America, including Canada. They are recognizable instantly because they include plus and minus signs, with the minus sign representing the favorite and the plus sign showing which side is the underdog.

Negative American Odds

Negative odds show you how much money must be wagered in order to win $100, excluding the initial bet amount.

Some examples of this include: 

  • Odds of -110 mean you must bet $110 to win $100 
  • Odds of -150 mean you must bet $150 to win $100 
  • Odds of -200 mean you must bet $200 to win $100

The higher the negative number is, the stronger the favorite is perceived to be.

Positive American odds

On the other end of the scale, odds with a positive sign show the size of the potential winnings from a $100 bet, not including the stake.

Some examples of this are: 

  • +100 returns $100 profit 
  • +150 returns $150 profit 
  • +300 returns $300 profit

Positive American odds are associated with underdogs and have higher potential returns to attract wagers.

Decimal Odds (The Global Standard)

Decimal odds are widely used around the world and are common at international sportsbooks. They are often considered easier to understand because they show the total return of the wager with a simple calculation: 

Stake size x Decimal odds = Total potential return

A few examples of this include: 

  • $20 at 2.00 returns $40 
  • $50 at 1.80 returns $90 
  • $10 at 3.50 returns $35

It’s worth mentioning that when using decimal odds, the potential return includes the initial stake size.

Fractional Odds (The Traditionalist)

The third most common format is fractional odds, which are traditionally used in UK betting markets and are especially familiar in horse racing.

As the name suggests, they appear as fractions such as 5/1, 2/1, or 10/11. These numbers show how much you stand to win relative to your stake, and the profit displayed does not include your original bet.

  • 5/1 means $5 in potential winnings for every $1 wagered (Total $6 return)
  • 2/1 means $2 in potential winnings for every $1 wagered (Total $3 return)
  • 10/11 means $10 in potential winnings for every $11 wagered (Total $21 return)

If you place a $20 bet at odds of 5/1, the potential winnings would be $100, excluding the initial stake, making the total return $120. Although fractional odds are less common in North American sportsbooks, they are still useful to understand.

 Implied Probability: The Math Behind the Curtain

Odds do more than determine potential winnings, as they also reflect the sportsbook’s estimate of probability. This concept is known as implied probability, which converts odds into a percentage that represents the likelihood of an outcome occurring.

  • +100 odds imply a 50 percent chance 
  • +300 odds imply about a 25 percent chance 
  • 2.00 decimal odds also imply a 50 percent chance

This conversion helps bettors to compare their own prediction with the sportsbook’s estimate. If a bettor believes an outcome has a higher probability than the odds suggest, they may consider the wager to offer value. 

 Why Do Odds Change? (The “Market” Factor)

sports betting odds explained

One thing that many bettors will notice is that sports betting odds do not stay the same from the moment they are posted.

Odds movements are a normal part of how betting markets operate, allowing sportsbooks to manage risk and keep markets competitive as conditions change.

Betting Activity and Market Balance

A major reason odds change is betting volume. If many bettors place wagers on one side of a game, the sportsbook may adjust the odds to attract bets on the opposite side.

For example, if an NFL game has a match in which many bettors are backing the favorite, the sportsbook may lower the payout for that team and increase the payout for the underdog. This encourages wagers on both sides and helps balance the sportsbook’s exposure to risk.

Injuries and Breaking News

When new information is released, betting odds can move quickly as a result. Sportsbooks monitor these developments and look out for how they may affect a team’s chances of winning. Some of the most common factors include: 

  • Injuries to key players
  • Late lineup announcements
  • Coaching decisions or roster changes
  • Weather conditions for outdoor sports 
  • Travel schedules or short rest periods

If a star player is ruled out shortly before a game, sportsbooks may adjust the odds to reflect the new expectations. This can also have an impact on live sports betting odds, for example, if a player is sent off the pitch for a serious foul.

Professional Betting Activity

Experienced bettors can also affect how odds shift during the week. When they believe the opening line offers good value, they often place their bets early.

Sportsbooks pay close attention to these wagers, especially when they come from bettors with a strong track record. If large bets come in, the bookmaker may quickly adjust the odds. As a result, the numbers posted early in the week can end up looking quite different from the closing odds just before the game begins.

Payout Practice: 3 Real-World Examples

Now that we’ve learned the basics of how betting odds work, let’s look at three real world examples with different probabilities of success:

The Safe Bet: Calculating a Heavy Favorite (-300)

Negative odds, such as -300 in this example, show a heavy favorite, which means bettors receive a lower return on their wager. For example:

  • Bet $30 at -300 odds
  • Total return is $40 ($10 in addition to the original wager)

The Coin Flip: Calculating Even Money (+100 or 2.00)

Should a match be considered as balanced, with either side having the same chance of success, the odds may be listed at +100 or 2.00 in decimal odds, also known as even money.

For example:

  • Bet $10 at +100 odds
  • Total return: $20 (In addition to the original wager)

With decimal odds, the same bet would look like:

  • Bet $10 at 2.00 odds.
  • Total return: $20 (Including the original stake size)

The Long Shot: Calculating a massive underdog (+500)

Last up, let’s look at how this would work when wagering on a massive underdog that has odds of +500.

  • Bet $10 at +500 odds.
  • Total return: $60 (Including stake)

When betting on a massive underdog, the potential winnings are much larger, but so is the risk due to the decreased probability of success.

Odds Across Different Betting Markets

It’s also worth mentioning that sports betting odds apply to a wide range of betting markets, and while the structure may change, the key concept does not. Some of the most common markets that you can find online include: 

  • Moneyline Bets: These involve predicting which side or player will win a game.
  • Point Spread Bets: A point spread wager includes a handicap between two teams.
  • Totals: This market revolves around the total score, often over or under a certain number.
  • Parlay Bets: A parlay bet combines multiple selections into the same wager, all of which must win for the bet to be successful.
  • Future Bets: These centre around long-term outcomes such as championship or tournament winners. 

While the markets can change across a variety of sports, the underlying odds and formats remain the same. This is true in all sports, including hockey betting, basketball betting, football betting, and soccer betting, to name just a few.

Final Whistle: Trust the Numbers, Play the Game

Sports betting odds are really just the sportsbook’s way of putting numbers on a game. They show which side is expected to win and how much you could get back if your bet lands. When a team is heavily favored, the payout is usually smaller. If the outcome is less likely, the odds are bigger and the reward increases.

For anyone starting out, learning how to read those odds makes a big difference. Once you get the hang of it, the numbers stop looking confusing and start giving you a quick snapshot of how a game is being priced.

Frequently Asked Questions About How Betting Odds Work

1 What is the difference between decimal and fractional odds?

Decimal odds show the potential winnings by multiplying the stake by the odds, while fractional odds show the potential winnings relative to the bet size.

2 Do odds work the same for live betting?

Yes, odds work the same when wagering on live sports, too.

3 What if the odds are the same for both teams?

Should the odds be the same for both sides of an event, this implies they both have an equal chance to win the game.

4 Why do odds change?

Odds can change for a variety of reasons, including a majority of bets being on one outcome, news such as injuries or weather changes, and professional bettors placing large wagers.