If you’re new to sports betting and asking yourself ‘How do betting odds work?’, you’ll find all the answers you need in our expert guide. Even if you’re a seasoned bettor, it’s good to understand the full ins and outs of betting lines and odds to top-up your knowledge and maximize your winning potential.

In this guide, we explain exactly how sports betting odds work for decimal, fractional and American odds, along with detailing the differences between sports. You’ll also be able to learn how to convert betting odds quickly, where odds come from and how you can use them to predict the most likely outcome in a sporting event.

What are Betting Odds?

Betting odds are the numbers on a sportsbook site that show how likely something is to occur in a match or event. Odds are set by the sportsbook and represent the overall probability of each possible outcome on a betting market.

The odds in any betting market are generally shown in one of three formats; fraction, decimal or American, whereby the number is accompanied by a plus or a minus (more on this later). However, regardless of which format you are viewing, they are all equal in terms of probable outcome and bet winnings.

In addition to showing the likeliness of an outcome, betting odds also allow you to work out the potential return from a bet based on your stake, including the amount wagered plus any profit.

What is the Difference Between Betting Odds and Lines?

The difference between odds and lines is that odds represent the chance of an outcome occurring, whereas lines are the projected margin between two competing teams.

Therefore, betting lines are the numbers specified by a sportsbook that can help handicap the game. In points spread betting, lines can be used to level the playing field between two teams and give you approximately a 50/50 chance to win the bet – creating betting opportunities on either side for bettors.

For example, in a NBA match between New York Knicks versus Washington Wizards, the points spread line is 6, with the favorite and underdog represented by -6 and +6 respectively. Meaning that the favorite must win by more than six points, or the underdog must not lose by more than six points in order for the bet to be successful. These line values are also accompanied by the odds of each outcome, such as -110.

However, in a moneyline bet where you simply pick the winner of the game, the line is always zero and the numbers shown are the odds.

betting odds and lines

About Bet Probability

Probability in betting is how likely an event or outcome is to happen. So how do betting odds work in terms of probability and why is it important? Every event outcome has a chance of occurring, whether it is high, low or equal. The higher the probability, the more likely it is to happen.

In some circumstances, the probability can be the same, or equal. For example, the probability of rolling a dice and getting any of the single numbers, is a one in six chance. Bettors can use odds to calculate the probability of possible outcomes as predicted by the sportsbook.

Calculating odds probability as a percentage

How do betting odds work for calculating probability as a percentage is a common question we are asked by new bettors. Percentages in betting are a simple way of looking at a sporting event to see which team is most likely to win.

You can calculate odds as a probability percentage using a formula that adds the fractional odds numbers together, divides them by one, then multiplied by 100.

For example, odds of 5/1 can be calculated as 1/(5+1) = 0.16 * 100 = 16% chance of occurring.

How do American Odds Work?

American odds are based around the theory of wagering $100 on any bet. The numbers are accompanied by a plus (+) or minus (-) sign and show you how much you can win if the bet is successful.

Bear in mind that you do not need to wager $100 and the odds can be used as a guide to work out potential returns, which is scaled up or down depending on your actual bet amount.

American odds are found on every betting line available and may vary based on the bet type, such as moneyline, points spread, total points, props and futures.

For example, if you are betting on the Kansas City Chiefs to win the NFL Super Bowl at odds of +300; for every $100 wagered you will win $300 as profit. The total bet return will be $400 ($300 profit plus your $100 stake).

How do Fractional Odds Work?

Fractional odds are most popular in the UK and parts of Europe, but are still commonly found in certain sports such as horse racing. The fractional odds format shows you the potential winnings from the bookmaker in relation to your stake.

So if you’re wondering how betting odds work in fractions, take a look at the following example:

Betting $1 on a horse to win the race at odds of 4/1 will payout $5 if it is successful. This total return is broken down as $4 profit plus your $1 stake.

Fractional odds where the first number is bigger than the second number are considered odds-against. If the first number is smaller than the second number it is considered odds-on and therefore more probable. Favorites in any fractional odds where two teams are competing are generally represented by the latter.

How do Decimal Odds Work?

Decimal odds are commonly found at European betting sites but are readily available at American and offshore-based sportsbooks too. They use a decimal number to display the returns you will get back if your bet is successful. Decimal odds are one of the easiest to use when calculating winnings because the amount returned includes your stake. So you simply multiply your stake by the given odds.

For example, if you bet $10 on Vegas Golden Knights in a NHL game at decimal odds of 4.5, you will win $45 if successful. The amount won includes your stake and can be broken down as $35 profit plus your $10 stake.

Where do Betting Odds Come From?

Betting odds at any modern online sportsbook come from odds compilers that either work for the company, or at a third-party partner. Depending on the bookmaker you are betting with, odds compilers can be manual analysts, automated systems, or a combination of both.

Odds are based on a variety of factors that influence the probability of an outcome and set the odds accordingly, including current form, previous results, team news and opponent.

For example, if a star goal-scorer in a soccer match is injured before a game takes place, the odds may be greater than they were intended to be because the probability of the team winning is now less likely.

When asking the question: how do betting odds work before and during events, you need to look at odds changes based on the weight of money moving around the market. If a team is attracting an unusual amount of attention and wagers, the sportsbook will generally make a move to reduce the odds, which in return reduces the margin and liability of the sportsbook.

What are Vegas Odds?

Las Vegas was the first state in the US to legalize sports betting and is considered the most accurate and up-to-date odds for the US market. For years, oddsmakers in Vegas have been the first and most trusted for establishing odds for various US sports and events, including football. Generally, when odds for NBA, NFL and MLB are published in Vegas, they move the betting lines for every bookmaker across the globe.

How Do Betting Odds Differ By Sport?

Now that we have a comprehensive answer to the question; how do betting odds work, along with recommended sportsbooks offering the best odds, it’s time to turn your focus towards how odds differ by sport. In the segment below, we have outlined six of the top sports in the US and highlighted the differences in odds based on event participants and available lines.


Without a doubt, wagering on football is one of the most popular sports for betting enthusiasts due to its size and depth. In the US, football is the juggernaut of sports betting as there are so many teams, players and lines to bet on. The odds and lines in football are generally geared around two teams playing against each other, with one team marked as the favorite and the other as the underdog.

The three most common odds in football are; the point spread representing the margin between the teams and how many points the favorite may win by, totals for the total points scored in a game overall (being under or over the given amount), and moneyline – a simple bet on which team will win the game. Additionally, football is also known for its props; which act as side-bets that are not reliant on the outcome of a game, such as total passing yards, and futures bets; whereby wagers are placed on a sporting event whose outcome will be settled ‘in the future’, such as the Super Bowl.


The odds for basketball are very similar to football and the main betting lines for each game are points spread, moneyline and total points over/under. The main difference here is that basketball teams play over 80 games throughout a regular campaign, so the odds can fluctuate rapidly from one week to another. Another noticeable difference in basketball is that each team in a standard game will typically score over 100 points, so the odds for spread betting and props can vary greatly. Example props include; first half points, team to score last, first shot of the game, largest lead in a game and both teams to score 100+ points.


Just as with football and basketball, baseball bettors have a wide array of betting options available during every game. However, bets are typically placed on the moneyline and the odds are given to the favorite and underdog based on who is most likely to achieve the most runs and win the game. One key difference in baseball betting is the runline instead of point spread. A runline bet is similar to a point spread, whereby a handicap is placed on the favorite or underdog in combination with moneyline-style odds. For example, a favorite runline bet of -1.5 (+150) means the team must win by at least two runs or more and in doing so the bet will be successful and return $150 profit for every $100 wagered.


Soccer betting lines work in a similar way to football but on a smaller scale. Soccer matches very rarely have more than three goals scored in total between both teams. Therefore the odds for totals are typically around the over/under 3 mark. Spread and moneyline bets are also available in soccer, along with plenty of props, including total passes/shots, total tackles, disciplinary cards, both teams to score, total corners, first/last goalscorer, clean sheet and double chance, where you can predict which team will win the game or draw.


Betting on hockey is big business for sportsbooks and bettors alike. So understanding how betting odds work is key to maximizing your returns and minimizing losses. Hockey and baseball are very alike, in the sense that you can wager on the total points in a game and moneyline. However, one core difference with hockey moneyline betting is that, unlike baseball, there are three potential outcomes instead of two; home win, away win and draw. Additionally, instead of a spread or runline, hockey has a puckline, whereby bets are typically based on a 1.5 points margin for either the underdog or favorite. Another popular bet in hockey is also the ‘Grand Salami’, when you bet on the total number of goals to be scored on any particular night, including under/over and away/home goals.


Betting on golf varies depending on the event or tournament that is taking place. There are plenty of betting lines and odds available ranging from the most common straight / outright betting wager, whereby you predict the winner of a tournament, such as the The Masters or US Open, through to matchup betting. In a golf matchup, one golfer goes up against another to score better over the course of a round or entire tournament, and you can place point spread and moneyline bets on these markets.

Best Markets at Sportsbooks

While you might think of simply betting on the outcome of a match as sports betting, there’s a lot more to bet on than just the final score. Here, we’ll cover some of the most popular markets you’ll find at top online betting sites.

  • Moneyline Bets: A moneyline bet is a bet on which team will win a match. This is the simplest and most popular type of bet among sports bettors.
  • Prop Bets: Prop bets are wagers on events that don’t directly impact which team will win. For example, a prop bet might let you wager on which team will be winning at halftime or on which player will score the most points.
  • Over/Under Bets: Over/under bets let you wager on whether some metric will be above or below a threshold set by the sportsbook. For example, you could bet on whether a team will score over or under a certain number of points.
  • Correct Score Bets: In a correct score bet, you’re wagering on a game’s final score. You must get each team’s score exactly right to win your bet.
  • Futures Bets: Futures bets are bets on events that will happen in the future – and not necessarily individual games. For example, you can place a bet on which team will win next season’s league championship or which player will be the league MVP.
  • Parlay Bets: Parlay bets let you combine 2 or more bets into a single wager. For example, you can bet that one team will win Game A, and another team will win Game B. For your bet to win, you must be right about both individual bets.
  • In-game Bets: In-game bets let you bet on sports live as the game unfolds. Odds are updated in real-time in response to the action. Live betting is popular because you can see how the game is going before placing a wager.


How do sports betting odds work?

Betting odds work by representing the probability of an outcome occurring in any sport. They are set by the sportsbook and allow you to calculate how much you will win if your bet is successful.

How do I read betting odds?

Reading betting odds is easy as they are either positive or negative and show what chance an outcome has of happening. You can convert odds into different formats so they are easier to read based on your preference.

What does +200 mean in odds?

Odds that come with a plus sign like +200 are generally underdog bets in a sport where 2 teams are going head-to-head. In this example, you will receive $200 profit for every $100 you bet. The total amount returned will be $300 (profit + wager).

How do plus and minus odds work?

A minus sign indicates that the outcome is more likely and the plus sign indicates a less likely outcome. Odds of +120 mean you will win $120 for every $100 wagered. Odds of -120 mean you will need to wager $120 in order to win $100.

What does it mean when odds are negative

Negative odds in American moneyline betting typically represents the favorite in a sport or event. You will need to wager more on an odds-on favorite in order to win $100 or more.

How Odds Work

For any wager, the payoff you’ll receive if you win is determined by the odds. Odds can be written in several different ways, but most US sportsbooks use American odds.

In this system, the favorite is indicated by a – sign and the number indicates the amount you need to wager to win $100. So, if the odds are -500 for a bet, you need to wager $500 to win $100. The underdog is indicated by a + sign and indicates the amount you’ll win for every $100 you wager. So, a +250 odds indicates that you would win $250 if you wager $100.

MyBookie-best sports Betting site

It’s also important to think about what odds you’re getting for any specific wager. The top sportsbooks typically offer competitive odds for big matches, but odds can start to look very different when betting on matches that don’t get a lot of attention.  Be sure to compare odds across a few top sportsbooks before placing a bet.

Odds Comparison Table

Use the table below to view different odds formats and how they represent the same probability of an outcome happening.

Decimal Fractional American Probability
1 0/∞ -∞ 100%
1.01 1/100 -10000 99.01%
1.02 1/50 -5000 98.04%
1.03 1/33 -3333 97.09%
1.04 1/25 -2500 96.15%
1.05 1/20 -2000 95.24%
1.06 1/16 -1667 94.34%
1.07 1/14 -1429 93.46%
1.08 1/13 -1250 92.59%
1.09 1/11 -1111 91.74%
1.1 1/10 -1000 90.91%
1.11 1/9 -909 90.09%
1.12 2/17 -833 89.29%
1.13 2/15 -769 88.5%
1.14 1/7 -714 87.72%
1.15 2/13 -667 86.96%
1.16 2/13 -625 86.21%
1.17 1/6 -588 85.47%
1.18 2/11 -556 84.75%
1.19 2/11 -526 84.03%
1.2 1/5 -500 83.33%
1.22 2/9 -455 81.97%
1.25 1/4 -400 80%
1.28 2/7 -357 78.13%
1.3 3/10 -333 76.92%
1.33 1/3 -303 75.19%
1.35 7/20 -286 74.07%
1.36 4/11 -278 73.53%
1.4 2/5 -250 71.43%
1.44 4/9 -227 69.44%
1.45 9/20 -222 68.97%
1.47 8/17 -213 68.03%
1.5 1/2 -200 66.67%
1.53 8/15 -189 65.36%
1.57 4/7 -175 63.69%
1.6 3/5 -167 62.5%
1.62 8/13 -161 61.73%
1.63 5/8 -159 61.35%
1.66 2/3 -152 60.24%
1.7 7/10 -143 58.82%
1.72 8/11 -139 58.14%
1.8 4/5 -125 55.56%
1.83 5/6 -120 54.64%
1.9 9/10 -111 52.63%
1.91 10/11 -110 52.36%
1.95 20/21 -105 51.28%
2 1/1 +/-100 50%
2.05 21/20 +105 48.78%
2.1 11/10 +110 47.62%
2.2 6/5 +120 45.45%
2.25 5/4 +125 44.44%
2.3 13/10 +130 43.48%
2.38 11/8 +138 42.02%
2.4 7/5 +140 41.67%
2.5 3/2 +150 40%
2.6 8/5 +160 38.46%
2.63 13/8 +163 38.02%
2.7 17/10 +170 37.04%
2.75 7/4 +175 36.36%
2.8 9/5 +180 35.71%
2.88 15/8 +188 34.72%
2.9 19/10 +190 34.48%
3 2/1 +200 33.33%
3.1 21/10 +210 32.26%
3.13 17/8 +213 31.95%
3.2 11/5 +220 31.25%
3.25 9/4 +225 30.77%
3.3 23/10 +230 30.3%
3.38 19/8 +238 29.59%
3.4 12/5 +240 29.41%
3.5 5/2 +250 28.57%
3.6 13/5 +260 27.78%
3.75 11/4 +275 26.67%
3.8 14/5 +280 26.32%
4 3/1 +300 25%
4.2 16/5 +320 23.81%
4.33 10/3 +333 23.09%
4.5 7/2 +350 22.22%
4.6 18/5 +360 21.74%
5 4/1 +400 20%
5.5 9/2 +450 18.18%
6 5/1 +500 16.67%
6.5 11/2 +550 15.38%
7 6/1 +600 14.29%
7.5 13/2 +650 13.33%
8 7/1 +700 12.5%
8.5 15/2 +750 11.76%
9 8/1 +800 11.11%
9.5 17/2 +850 10.53%
10 9/1 +900 10%
11 10/1 +1000 9.09%
20 19/1 +1900 5%
30 30/1 +2900 3.33%
40 40/1 +3900 2.5%
50 50/1 +4900 2%
60 60/1 +5900 1.67%
70 70/1 +6900 1.43%
80 80/1 +7900 1.25%
90 90/1 +8900 1.11%
100 100/1 +9900 1%
1000 1000/1 +99900 0.1%
Author photo
Alan Kendall
Sports Editor

Alan Kendall joined Basketball Insiders in January, 2023 with over fifteen years of experience writing about online sports betting. He is an experienced writer with a strong interest in the NBA, NFL, NHL and UFC. Alan brings a wealth of knowledge to every piece he contributes to and has written for many publications including Augusta Free Press and The Sports Daily.

All posts by Alan Kendall
Author photo
Alan Kendall Sports Editor

Alan Kendall joined Basketball Insiders in January, 2023 with over fifteen years of experience writing about online sports betting. He is an experienced writer with a strong interest in the NBA, NFL, NHL and UFC. Alan brings a wealth of knowledge to every piece he contributes to and has written for many publications including Augusta Free Press and The Sports Daily.

All posts by Alan Kendall