Sports Betting Odds: How Betting Lines Work

As legal sports betting spreads across the United States, more Americans want to know how betting odds work. Our introduction to sports odds teaches people how to read sports betting odds, including American, fractional, and decimal odds. We discuss the difference between moneyline bets, point spreads, over/under bets, and futures betting. Finally, we answer the main questions US sports bettors have about regulated and unregulated online sports betting sites.

How Do Betting Odds Work?

Online sportsbooks provide odds on a world full of sporting events. While US bettors prefer American odds, people should know the three types of odds. Some sports, such as horse racing, feature alternative odds systems that you’ll want to understand.

American Odds

American odds are familiar to US sports bettors. Thus, they’re easy to learn and use for many American gamblers. The favorite has a minus (-) prefix, so a basic bet on the favorite is -110. Meanwhile, the underdog’s odds feature a plus prefix (+). Therefore, an underdog’s odds might be written as +125, +200, or +500.

The notation system is based on a $100 wager. Certainly, bettors aren’t required to make $100 wagers, but figuring payouts is easiest when considering a $100 bet.

For a +125 underdog, the bettor would win a $125 payout if they won a $100 bet. Conversely, if you bet on a -110 favorite, the bettor must make a $110 bet in order to win $100. Or if you bet $100, you would win a bit above $90 if you won a bet on a favorite.

Fractional Odds

Fractional odds are also known as British odds, and they are often used for horse racing bets. At the racetrack, you’ll often see these posted on odds boards or tote boards with a backslash or hyphen.

For example, if you see a bet on the 2023 Kentucky Derby winner, Mage, the bet would be listed as 8/1 or 8-1 to win the next race. If Mage won the race, then you would win $8 for every $1 you wagered.

At the same time, if the fractional odds were reversed to 1/8 or 1-8., then you’d need to bet $8 for every $1 you hoped to win. Obviously, Mage would have to be an overwhelming favorite for such odds to be posted.

Decimal Odds

The third major form of odds is decimal odds, also known as continental odds. These are easy to use because you can calculate payouts by multiplying the odds by the wager.

If you made a 1.40 decimal odds favorite, this would translate to a -250 moneyline favorite in American odds. If you bet $100 in this system and won, then you would win $40 plus the original wager of $100. The payout would be $140 — which indicates again that you’re betting on a big favorite.

US Sports Betting Odds Explained

When a sporting event is posted in an online sportsbook, the game or match has three major types of odds posted next to it. These are moneyline bets, point spreads, and over/under bets. Each betting type needs its own explanation.

Moneyline Bets

For people who don’t want to do with final scores and point spreads, moneyline betting is the best. A moneyline bet is as simple as it gets. You bet on the winner.

To bet on a favorite, you’ll need to lay more money than you receive on the payout. If you want to bet on the underdog, you receive a much bigger payout, because you expect the underdog to win outright. Moneyline bets don’t pay as often on the underdog, so the payouts are big.

Example of a Moneyline Bet: Let’s say the Buffalo Bills are favorites to beat the Miami Dolphins. The Bills might be listed at -150 while the Dolphins are listed at +140. You’d have to bet $150 to win $100 as a Bills bettor, while you’d receive a $140 payout on a $100 bet if you bet the Dolphins. Unlike the decimal odds above, you’d receive a $140 payout plus your original $100 bet back.

Point Spread Bets

Moneyline bets are easy, but they don’t create much action when one team is a big underdog. Most years, if the Alabama Crimson Tide are playing the Kentucky Wildcats, Vanderbilt Commodores, or Texas A&M Aggies in football, they would be huge favorites. A moneyline bet doesn’t work for that situation, so sportsbooks offer point spreads.

With point spread odds, the bookmaker assigns a handicap to the favorite. If Alabama is playing Texas A&M, the Crimson Tide might receive a 30-point handicap. To indicate this handicap, a sportsbook would show Alabama (-30) versus Texas A&M (+30). To determine the winner of the bet, you would either subtract 30 points from Alabama’s score or add 30 points to the Aggies’ score.

If Alabama won 34-3, then you would subtract 30 from their score to make it 4-3 — Alabama wins. But if Alabama won 34-7, then the point spread result would be 4-7 — Alabama would have failed to cover and the Aggies would win the bet. Obviously, if the Aggies won outright, the bettor on the underdog wins a point spread bet.

Over/Under Point Total Bets

Sometimes, you don’t feel comfortable picking a winner. Instead, you have a sense of what kind of a game will be played. For instance, you might expect a high-scoring shootout or a gritty defensive struggle. Maybe key offensive or defense stars are out, or maybe the weather will affect play.

In either case, you want in this scenario to make a “totals” bet. Often, this is called an over/under bet. The bookmaker sets a line on the total combined points in the game or match. For instance, a bookmaker might set a line of 49.5 on the combined score.

If the teams combine for 50 or more points, then the “over” wins. If the teams score 49 or fewer total points, then the “under” proposition wins. Totals betting is great in other instances, of course. Commonly, they are the second leg in a same-game parlay bet. The bettor picks a winner and an over/under total, and both bets must win for the gambler to win.

More US Sports Betting Odds Explained

Those are the broad types of sports betting odds, but many others exist. For a snapshot of the other bets you’ll find at online sportsbooks, browse through the following glossary.

Futures Betting

These are season-long bets. They can be on the league champion or who wins the pennant in MLB betting. If you think one team is going to win a league title, that’s when you make a futures bet. The advantage is the payouts are high even for favorites, because it’s that team against the field.

Prop Betting

Proposition bets are about a single action or event within a game. Examples include who will score the next touchdown, whether someone hits a home run, or how many 3-pointers a player scores. Prop bets also include entertainment awards, politics, or the National Anthem before the Super Bowl.

Live Betting

In-game betting is when a sportsbook posts betting odds in real-time during an ongoing game. In-play bets might be team props, game props, player props, or totals. Unlike traditional pre-game betting, live betting lets you make multiple wagers during a game.

1st Half Bet: A common in-play bet is on the score after the 1st half of an NFL or NBA game. In NHL betting, it might be a 1st Period or 2nd Period bet. Baseball has 5th Inning bets or other variants.
Halftime Bet: Another in-play bet, but in this case one made at halftime of a game. If the Chargers are up 17-14 at halftime but you think the Chiefs will win in the end, you make a halftime bet on the in-game betting page.

How to Make Parlay Bets

Sportsbooks offer a lot of different parlay bets. Because several 50/50 wagers must hit in order to win, bookmakers love for bettors to make these wagers. They offer big payouts, so many bettors take up the challenge. When you do, you’ll find several types of parlays.

Parlay Bets: Connecting two or more bets into a single wager. Often between 2 and 10 legs, but can be more at some sportsbooks. Parlay bets don’t hit as often but offer bigger payouts when they do.
Same-Game Parlays: All the legs are based on one game. Some betting propositions are not allowed because they are betting on the same outcome. For instance, you might not be able to make a 1st Half and Full-Game bet on the same team.
Teaser Bets: A parlay where buy points and move the line in the bettors’ favor. The typical teaser bet is a 2-leg, 6-point teaser. Hence, you might move the Chiefs from a -9 favorite to a -3 favorite and the Bengals from a -7 favorite to a -1 favorite.
Pleaser Bet: A parlay where the line is moved in the sportsbooks’ favor. In return, you receive a higher payout if you win. Conversely, the Chiefs (-9) would go to the Chiefs (-15) and the Bengals (-7) would become the Bengals (-13). Again, the advantage is a much bigger payout if both hit.

What is a Progressive Parlay?

Some sportsbooks offer progressive parlays, where you still win if one or more legs lose. Typically, this would be 1 loss on a 2 to 4-leg parlay, 2 losses on a 5 to 8-leg parlay, and 3 losses on a 9 to 12-leg parlay. Online sportsbooks vary on the rules for these.

What is an If Bet?

An “If Bet” is similar to a parlay, but it usually connects 2 to 6 bets, which are contingent on one another. This might seem like a parlay, but it allows the payout from the first winning bet to be applied to the 2nd leg. Again, the advantage is a higher payout.

Sports Betting Odds FAQ

What are sports betting odds?

Odds are implied probabilities created by sportsbooks to convince bettors to make a wager. When you see odds, they give an indication of the bookmaker’s opinion on the game, but also the payout if you win.

How do I read sports betting odds?

That depends on whether you’re reading American odds, fractional odds, or decimal odds. Most US sports bettors use American odds, which are based on the payout you’d receive if you bet $100. For instance, +200 odds mean you’d win $200 (plus the original $100) if you made a $100 bet on an underdog.

What does +/- mean in betting odds?

The (+) indicates the underdog and the (-) indicates the favorite. Bookmakers derived the notation system from point spread betting, which handicaps a game by taking points away from the favorite or adding points to an underdog’s total. Even in moneyline betting, the plus or minus symbol indicates who is the favorite or who is the underdog.

What are the different types of sports betting odds?

They are American odds, fractional odds (British odds), or decimal odds (continental odds). American odds are what you’ll see the most at US online sportsbooks, but you can switch these to fraction or decimal odds if these work better for you. Often, you’ll find fractional odds in racebook betting. Decimal odds make it easy to calculate your payouts.

How do I bet on scores and odds?

If you want to bet on final scores, you should make over/under bets. Total bets are based on the total number of points, runs, or goals scored in a game.

What kind of events do people bet on?

Name a sporting event and people bet on it. In fact, people bet on more than sporting events: they’ll bet on entertainment, politics, awards ceremonies, or pop culture events. For instance, some UK sportsbooks offer odds on whether UFOs will land in the next year. On Super Bowl weekend, you’ll find odds posted on the length of the National Anthem or the color of the Gatorade poured on the winning coach.

For the most part, Americans bet on American football, basketball, baseball, hockey, or UFC. They also might bet on European football (Association football or soccer), golf, tennis, cricket, or boxing. Furthermore, the biggest sportsbooks offer odds on darts, bowling, or Esports.

How do I calculate my potential winning from sports betting?

Again, that depends on the type of odds you’re using and the type of bets you’re making. American odds are most common at US sportsbooks, and they are based on whether the team or player is the favorite or underdog.

The best US online sportsbooks provide payout information on the bet slip. When you visit an online sportsbook’s homepage or the live in-game betting page, you’ll see a link that says “Bet Slip”. Click on the link and add the game, the bet type you prefer, and the wager amount.

Once you do, the bet slip should calculate your potential winnings.

Where do I find updated scores and odds?

Online sportsbooks update scores as games happen. Once you’re on the main sports betting page or the game page, the site updates the scores until the game ends. If you use the “Live Betting” page or in-game betting option, it updates the scores AND the odds as the game takes place.