Sports betting refers to placing money on the outcome of sporting events or specific moments within those events. It has expanded into a multi-billion-dollar global industry, which includes traditional bookmakers, online sportsbooks, betting exchanges and mobile-app platforms.
Understanding Sports Betting Odds And How To Read Them
For newcomers, the numbers on a betting slip or sportsbook app can look unfamiliar. The first step towards confidence is learning how odds work and what they represent. Different regions present odds in different formats, and each system communicates probability and payouts in its own way.
According to The Athletic, there are three common formats used worldwide:
American odds
Fractional odds
Decimal odds
American Odds
American odds are based on a $100 reference point, but the relationship with that number depends on whether the selection is a favourite or an underdog.
Minus (–) Odds For Favourites: When a selection is the favourite, the odds appear with a minus sign. This figure shows how much you must stake to win $100. For example, –110, a common spread price, means you need to bet $110 to make a $100 profit, giving you a total return of $210. At –200, you would have to stake $200 to win $100. The same ratios apply to smaller bets. So, a $10 stake at –200 would return $15 in total, which is your $10 stake plus $5 profit.
Plus (+) Odds For Underdogs: A plus sign indicates an underdog. These odds show how much profit you would earn from a $100 stake. With +200, a $100 bet would produce a $200 profit, returning $300 overall. Scaled down, a $20 stake at +200 would yield a $40 profit plus your original $20.
Even-Money Odds: Even-money prices are shown as –100, +100 or EV, and signal that the potential profit is equal to the stake. They tend to appear far less frequently than other odds formats.
Fractional Odds
Fractional odds are widely used in the UK and other markets outside the US, though some American sportsbooks also display them. As the name suggests, they appear as fractions, for example 3/1 or 7/4. The profit is calculated by multiplying your stake by the fraction.
A $10 bet at 3/1 would generate a $30 profit, with your original $10 returned.
For something less straightforward, such as 7/4, the calculation is just as simple. Multiply your $10 stake by the numerator (7) and then divide by the denominator (4). That gives you $17.50 profit, plus your $10 stake.
The relationship between the numbers signals whether a selection is a favourite or an underdog.
Favourites have a larger denominator (e.g., 1/2, 2/5). Underdogs have a larger numerator (e.g., 3/1, 7/4).
Decimal Odds
Decimal odds are displayed as a single number. That number tells you the total amount you’ll get back for every $1 you bet. So, if the odds are 6.0, a $1 winning bet returns $6 in total, which is $5 profit plus your original $1.
Decimal odds are widely used across Europe and other regions because they make calculations straightforward, especially when fractional odds become too complicated. For example, American odds of –115 convert to a messy fractional form of 20/23. Working out potential returns using 20/23 for a $10 bet isn’t exactly fun. But with decimal odds, the same bet is listed as 1.87. Just multiply $10 by 1.87, and you instantly know you’d get $18.70 back, including your stake. It’s faster, cleaner and generally easier for most bettors to understand.
Converting Odds To A Break-Even Percentage
No matter the format, converting odds into a break-even percentage is essential to knowing whether a bet is worthwhile. It shows the minimum chance a bet needs to succeed for you to avoid losing money.
For example, a +200 moneyline means a $100 bet would earn $200 profit, giving a total return of $300. To calculate the implied probability, divide 100 by the sum of the odds plus 100: 100 ÷ (200 + 100) = 33.33%.
This means the bookmaker believes the outcome has about a one-in-three chance of happening. If you assess the real chance as higher than that, the bet offers value.
Why This Matters
Think of it like a coin flip. You know there’s a 50% chance of heads. If the odds offered imply less than that, it’s a favourable bet. Sports aren’t as simple as coins, but the principle is the same. Comparing the implied probability with your own estimate is a key step in spotting good moneyline bets.
Legal Landscape
Sports betting in the UK is governed by The Gambling Act 2005, which provides a definition of betting and empowers The UK Gambling Commission to regulate sports betting in the country. The three licencing objectives of The Gambling Act 2005 include preventing gambling from being associated with crime, promoting fairness in gambling and protecting vulnerable individuals, specifically children.
United States
In the United States, the Professional and Amateur Sports Protection Act (PASPA) previously prohibited states from legalising sports betting. But now states have the right to legalise and regulate sports wagering after the Supreme Court invalidated PASPA in 2018. As of November 2025, a total of 38 states in the United States, along with Washington, D.C. and Puerto Rico, have made sports betting legal in some way. Among them, 30 allow online sports betting through mobile apps or online platforms. Additionally, sports betting in online platforms in Washington, D.C. and Puerto Rico is legal.
European Union And Malta
The European Union does not have a single, unified gambling law. Each member state has the power to control licencing within their boundaries. However, EU directives on anti-money laundering (AML) and data protection are gradually promoting some convergence across jurisdictions. Europe’s online gaming market is substantial, valued at over €28 billion, with countries like Sweden and Malta emerging as key regulatory and operational centres for the industry.
Australia
In Australia, both federal and state regulations govern gambling. The Interactive Gambling Act of 2001 prohibits various kinds of online gambling activities such as casino games and live sports betting, while licensed online sports wagering is allowed. The regulations are enforced through the efforts of the ACMA and AUSTRAC. High-profile enforcement ensure that the activities conform to financial crime regulations.
India
In August 2025, Parliament passed the Promotion and Regulation of Online Gaming Bill, effectively banning online gambling after government data revealed companies were extracting $2.3 billion annually from 450 million users. The law targets platforms offering card games, poker and fantasy sports, criminalising their promotion, financing and operation, with offenders facing up to five years in prison. While India’s gaming industry remains one of the largest globally, the legislation exempts e-sports and educational games, which the government intends to promote as part of its digital economy initiatives.
As online and mobile betting regulations continue to change, staying informed about regulatory guidance and local laws is essential for everyone involved.