If you’re new to sports betting, the numbers and symbols in odds can look like a secret language. But once you understand them, betting odds become a helpful tool for making more confident, informed wagers. They tell you two important things: how much you can win and how likely an outcome is—at least in the bookmaker’s eyes.
In this guide, we’ll walk through the three main sports betting odds formats—decimal, fractional, and American—using real examples from football, horse racing, and tennis. We’ll also explore how to work out the likelihood an event will happen, the difference between value bets and long shots, and how to read shifts in the market to your advantage.
1. Decimal Odds
Decimal odds are one of the simplest formats to understand and are widely used across Europe, Australia, and Canada. They show the total return for every unit you stake, meaning your profit plus your original bet.
For example, if a football team is priced at 2.50 to win, and you place a £10 bet, you’d get a total of £25 back if they win—£15 profit plus your £10 stake.
In horse racing, a horse priced at 4.00 means a £5 bet would return £20 in total. In tennis, backing a player at 1.80 with a £20 stake would return £36. Decimal odds are straightforward and make it easy to compare potential returns quickly.
2. Fractional Odds
Fractional odds are traditional in the UK and Ireland, particularly popular for horse racing. Written as a fraction like 5/2, the first number shows how much you’d win in profit compared to the amount you stake (the second number).
For example, in football, if Arsenal are 5/2 to win and you bet £10, your profit would be £25, plus you’d get your stake back for a total return of £35.
In horse racing, if a runner is 7/4 and you stake £20, your profit would be £35, and your total return would be £55. In tennis, odds of 4/5 mean you’d win less than your stake, but the likelihood of winning is considered higher.
3. American Odds
American odds work differently and are most common in the United States. They use either a plus (+) or minus (–) sign.
A positive number, like +150, tells you how much profit you’d make from a £100 bet. For instance, +150 in football means a £100 bet would give £150 profit plus your stake back.
A negative number, like –200, shows how much you need to stake to make £100 profit. So, in horse racing, if a horse is –200, you’d need to stake £200 to win £100 profit. In tennis, a player at –120 would require a £120 bet to win £100 profit.
4. Understanding Implied Probability
Odds don’t just show potential payouts—they also reflect the bookmaker’s estimation of how likely an outcome is. This is known as implied probability.
For instance, decimal odds of 2.50 suggest about a 40% chance of winning. Fractional odds of 5/2 suggest just under 30%. The shorter the odds, the higher the implied chance of winning, while longer odds mean the bookmaker believes the outcome is less likely.
Understanding this helps you decide if a bet offers good value. If you think an event is more likely than the odds suggest, you may have found a value bet.
5. Value Bets vs. Long Shots
Value bets happen when you believe the true chance of an outcome is higher than what the odds indicate. For example, if you think a team has a 50% chance of winning but the odds suggest only 40%, that’s a value bet.
Long shots are the opposite—big payouts for unlikely outcomes. They can be tempting, such as a horse at 50/1, but with such low chances, they’re more for occasional fun than consistent profit.
6. Why Odds Change
Odds aren’t fixed—they move based on market activity and new information. Bookmakers may shorten odds (make them smaller) if a lot of money comes in for one side to limit their potential losses.
In football, if a star striker is suddenly ruled out due to injury, the odds on their team might drift (get longer), while the opponent’s odds shorten. In horse racing, a sudden change in the weather could favour certain runners, shifting prices. In tennis, an injury during warm-up can cause dramatic odds changes before a match begins.
7. Reading Odds Movement
Watching how odds move can give you clues about what’s happening behind the scenes.
- Early moves can indicate sharp bettors getting in before major news breaks.
- Steamers are outcomes where odds shorten quickly, often due to heavy backing.
- Drifters are outcomes where odds lengthen, suggesting confidence in them is fading.
Comparing prices across the best online betting sites can help you see where the consensus is forming. If all bookmakers shift in the same direction, it’s usually due to new and significant information. However, be careful not to overreact to hype—sometimes odds swing too far and create fresh value elsewhere.
8. Practical Tips for Beginners
- Start with decimal odds – they’re the easiest to understand.
- Compare odds before betting – a small difference in price can mean more profit over time.
- Keep records – tracking your bets can help spot patterns in your wins and losses.
- Use research alongside odds – form, stats, and news are just as important.
- Don’t chase long shots – balance fun with realistic expectations.
Final Thoughts
Betting odds aren’t as complicated as they first appear. Whether you’re looking at a football match, a horse race, or a tennis tournament, knowing how to read decimal, fractional, and American odds gives you a strong foundation for betting smarter.
By understanding implied probability, recognising value bets, and learning to read odds movements, you’ll make more informed decisions—and enjoy the betting experience more. And while no system guarantees wins, using the odds wisely, shopping around the best online betting sites, and staying disciplined can give you a real edge.