By Niamh Gallagher · Last updated November 2026Odds are a price. That’s really all they are. A bookie looks at a match or a race, decides how likely each outcome is, shaves a bit off for themselves, and shows you the result as a number.
If you’ve ever stared at 13/8 and wondered what on earth it means, you’re in good company. This is betting odds explained without the jargon: the two formats you’ll see in Ireland, how to switch between them, and the one idea that changes how you look at every price, which is implied probability.
How Do Betting Odds Work? Every Price Answers Two Questions
Every set of odds answers two questions at once. The first is practical: if I win, how much do I get back for my stake? The second: how likely does the bookie think this is?
Short odds, like 1/3, mean the bookie thinks something is very likely and will pay you little for being right. Long odds, like 20/1, mean they think it’s a long shot and will pay you a lot if it comes off. The two formats below are just different ways of writing the same price, and once you can read both you can compare any bookie with any other.
Fractional Odds: Reading 13/8 Over the Bookies’ Counter
Fractional odds are the traditional format in Irish and British racing, and you’ll still hear them called out in every bookies on a Saturday. The fraction shows your profit compared with your stake.
- 5/1 (“five to one”): win €5 for every €1 staked. A €10 bet makes €50 profit, and with your €10 back that’s €60.
- 1/2 (“two to one on”): win €1 for every €2 staked. A €10 bet makes €5 profit, so it returns €15.
- 1/1 (“evens”): win the same as you stake. €10 returns €20.
Odds-on, odds-against and evens
When the first number is bigger than the second (5/1, 6/4), the price is odds-against, and you win more than you stake. When the first number is smaller (1/2, 4/6), it’s odds-on, and you win less than your stake because the bookie thinks it’s more likely to happen than not.
Where 11/8 and 15/8 come from
Some prices look odd: 11/8, 13/8, 15/8, 10/11. They exist because odds move in small steps between the round numbers. You don’t need to memorise them. Divide the top number by the bottom to see what you win per €1. 13/8 is 1.625, so €10 at 13/8 makes €16.25 profit and returns €26.25. 10/11 is about 0.91, so €10 returns roughly €19.09.
Decimal Odds: The Format Your App Prefers
Decimal odds are standard across Europe and on most betting apps, and a lot of punters find them easier. I’d agree. The number shows your total return for every €1 staked, stake included.
- 6.00: a €10 bet returns €60 (€50 profit plus your €10).
- 1.50: a €10 bet returns €15.
- 2.00: evens, so €10 returns €20.
To get your profit, take one off the decimal and multiply by your stake. At 2.63, €10 returns €26.30, which is €16.30 profit.
Swapping 6/4 for 2.50 and back again
The conversion is easy: decimal odds equal the fraction worked out as a number, plus one. So 5/1 is 5 + 1 = 6.00. 6/4 is 1.5 + 1 = 2.50. 1/2 is 0.5 + 1 = 1.50. And 13/8 is 1.625 + 1, which most apps round to 2.63, the number in this guide’s title.
Going the other way, take one off the decimal and turn what’s left into a fraction. 3.25 becomes 2.25, which is 9/4.
The Percentage Hiding Inside Every Price
This is the bit most guides skip, and it’s the most useful thing on this page. Every price carries an implied probability, the chance of winning the bookie is pricing in. To work it out, divide 1 by the decimal odds. Odds of 2.00 imply 1 ÷ 2 = 50%. Odds of 4.00 imply 25%.
| Fractional odds | Decimal odds | Implied probability | Return on a €10 stake |
|---|---|---|---|
| 1/4 | 1.25 | 80% | €12.50 |
| 1/2 | 1.50 | 66.7% | €15.00 |
| 1/1 (evens) | 2.00 | 50% | €20.00 |
| 6/4 | 2.50 | 40% | €25.00 |
| 2/1 | 3.00 | 33.3% | €30.00 |
| 5/1 | 6.00 | 16.7% | €60.00 |
| 10/1 | 11.00 | 9.1% | €110.00 |
Once you think in percentages, betting gets a lot clearer. If you reckon Munster have a better than 40% chance of winning and you can get 6/4, that’s a bet worth considering. If you think it’s nearer 30%, the price is too short and you should leave it alone.
Where the Bookie’s 7% Lives
Add up the implied probabilities of every outcome in a market and you’ll get more than 100%. That extra is the bookie’s margin, also called the overround.
Take a football match priced like this:
- Home win 6/4 (2.50): 40%
- Draw 9/4 (3.25): 30.8%
- Away win 7/4 (2.75): 36.4%
That adds up to about 107%. The extra 7% is how the bookie makes money whatever the result. A two-way market shows it even more clearly. If both sides are 10/11 (about 1.91), each implies roughly 52.4%, so the book adds up to around 105%. In a fair world, both would be evens.
The lower the margin, the better the deal for you. Margins tend to be tighter on big events like a Premier League Sunday and wider on niche markets and long-range outrights.
Fractions on the Board, Decimals on the App
In Ireland you’ll come across both formats. Racing commentary, the boards in the bookies and the newspaper racecards lean on fractional odds. Most apps let you switch between fractional and decimal in your settings. If you’re choosing between Irish betting sites, it’s worth checking how easy that switch is, because comparing prices across bookies is much quicker in decimal.
You might also run into American odds (+150, −200) on US sports. A positive number shows the profit on a 100 stake, so +150 is the same as 6/4 or 2.50. A negative number shows what you’d stake to win 100, so −200 is the same as 1/2 or 1.50.
Five Questions I Ask Before Taking Any Price
- What chance would I give this? I put a rough percentage on it before I look at the odds, then compare with the implied probability.
- Is it shorter elsewhere? A 2/1 shot at one bookie might be 9/4 at another. Over a season, that adds up to a fair whack.
- Am I reading decimal or fractional? There’s no prize for doing mental arithmetic on 15/8 in a hurry. I switch to decimal if fractions slow me down.
- How big is the margin in this market? Big prices on outrights and specials often carry the fattest margins.
- Does “short” mean “safe”? No. A 1/4 shot still loses one time in five on its own implied numbers.
FAQ
What do odds of 5/1 mean?
For every €1 you stake, you win €5 profit. A €10 bet at 5/1 returns €60, including your stake.
How do I convert fractional odds to decimal?
Divide the first number by the second, then add one. So 6/4 becomes 1.5 + 1, which is 2.50.
What is implied probability?
It’s the chance of an outcome that the odds suggest. Divide 1 by the decimal odds, so 4.00 implies 25%.
Are decimal or fractional odds better?
Neither gives you better value; they’re the same price written differently. Decimal is usually quicker for comparing and working out returns.
Whatever format you prefer, set a budget and stick to it. Free, confidential help is there if you need it: visit gamblingcare.ie or ring Gambling Care on 1800 753 753.