Fractional and decimal odds explained for Irish bettors

Every price a bookmaker shows does two jobs. It tells you how much a bet would return if it wins, and it signals how likely the bookmaker considers the outcome. A horse at 10/1 is seen as less likely to win than one at 2/1. A team at 1.30 is a strong favourite; a team at 6.00 is not.

In Ireland you will meet two formats every day. Fractional odds (7/2, 5/1, evens) are traditional in Irish and British racing and are still used on racecards, in betting shops and by commentators. Decimal odds (4.50, 6.00, 2.00) are common on betting websites and apps and are often the default there. Most bookmakers let you switch between the two in your account settings. American odds (+350, −200) turn up now and then, mostly on US sports.

Whatever the format, the price underneath is identical. 7/2 and 4.50 describe exactly the same bet with exactly the same return. Once that clicks, everything else on this page is simple arithmetic, and the examples use a €10 stake so you can follow the sums.

A fractional price compares what you win with what you stake. The number on the right is the stake; the number on the left is the winnings. At 7/2 (“seven to two”), every €2 staked wins €7 if the bet wins, and your stake comes back on top.

So a €10 bet at 7/2 returns €45 if it wins: €35 in winnings (€10 × 7 ÷ 2) plus your €10 stake. If it loses, the €10 is gone.

Reading prices aloud

Prices have their own spoken form. 5/1 is “five to one”. 9/4 is “nine to four”. 11/10 is “eleven to ten”. A short price such as 1/2 is often said as “two to one on”, because the outcome is odds-on. Even money, written “evens” or “EVS”, means 1/1: you win €1 for every €1 staked.

Why the odd-looking fractions?

Prices such as 11/8, 13/8, 15/8 and 100/30 come from the traditional ladder of prices used on racecourses. They fill the gaps between round numbers: 13/8 sits between 6/4 and 7/4, and 100/30 is a little longer than 3/1. You don't need to memorise them. Converting to decimal, as shown below, makes them easy to compare.

The formula

Winnings = stake × (left number ÷ right number). Total return = winnings + stake.

A decimal price shows the total return for every €1 staked, with the stake already included. At 4.50, each €1 returns €4.50 if the bet wins: €3.50 in winnings plus your €1 back.

That makes the sum shorter. Total return = stake × decimal odds. A €10 bet at 4.50 returns €45 if it wins, and the winnings are €45 − €10 = €35. It is the same result as 7/2, because it is the same price.

Decimal odds are also easier to compare at a glance. 2.63 is clearly bigger than 2.50, which is less obvious written as 13/8 and 6/4. The smallest decimal price is just above 1.00: at 1.01 you would win one cent for every euro staked. Evens is 2.00, and anything below 2.00 is odds-on.

The formula

Total return = stake × decimal odds. Winnings = total return − stake.

American (or moneyline) odds use a plus or minus sign around a base of 100. A plus number shows what a €100 stake would win: +350 means €100 wins €350, the same price as 7/2 or 4.50. A minus number shows what you would need to stake to win €100: −200 means a €200 stake wins €100, the same as 1/2 or 1.50. Evens is +100.

You will rarely need this format in Ireland. If an app offers it, it converts like this: for plus odds, decimal = 1 + (number ÷ 100); for minus odds, decimal = 1 + (100 ÷ the number without its minus sign).

Fractional to decimal: divide the left number by the right number, then add 1. 7/2 becomes 3.5 + 1 = 4.50. 4/6 becomes 0.667 + 1 = 1.67.

Decimal to fractional: subtract 1, then write what is left as a fraction. 3.25 becomes 2.25, which is 9/4. 1.80 becomes 0.80, which is 4/5. Bookmakers round decimal prices to two places, so a converted price can look slightly different: 4/6 shows as 1.67, not 1.666…

The table covers the prices you will see most often. The last column is the implied probability, explained in the next chapter.

Implied probability turns a price into a percentage: the chance of the outcome that the price suggests. With decimal odds the formula is: implied probability = 1 ÷ decimal odds × 100. With a fractional price a/b, it is b ÷ (a + b) × 100.

Take 7/2. That is 2 ÷ (7 + 2) = 0.222, or about 22.2%. The decimal version gives the same answer: 1 ÷ 4.50 = 0.222. Evens is 50%, 1/2 is 66.7% and 10/1 is 9.1%.

Two points matter here. First, implied probability is the bookmaker's price, not a fact about the event. Nobody knows the true chance of a horse winning or a team covering a handicap. Second, if you add up the implied probabilities of every outcome in a market, the total comes to more than 100%. The extra is the bookmaker's margin, which we cover briefly below.

Comparing an implied probability with your own view can help you understand what a price is saying. It does not make any bet more likely to win, and most bets lose.

Odds-against means the winnings would be bigger than the stake: 2/1, 5/1, 3.00, 6.00. The price suggests the outcome is less likely to happen than not.

Odds-on means the winnings would be smaller than the stake: 1/2, 4/6, 1.50, 1.67. The price suggests the outcome is more likely than not, but more likely is not certain. Odds-on favourites are beaten regularly, and when they are, the whole stake is lost. A €10 bet at 1/2 wins €5 if it wins and loses €10 if it doesn't.

Evens (1/1, 2.00, +100) sits between the two: the winnings equal the stake, so a €10 bet at evens returns €20 if it wins.

The language around prices

The favourite is the shortest price in a market. Two or more runners on the same shortest price are joint-favourites or co-favourites. A big price is an outsider or a long shot. A price shortens when it gets smaller, say from 5/1 to 3/1, and drifts or lengthens when it gets bigger. You will hear all of these on racing commentary and see them in our betting glossary.

Here is what a €10 single would return at a range of prices, if the bet wins. The final column is what happens far more often across all bets: the stake is lost.

Each-way bets

An each-way bet is two bets: one to win and one to place, so “€10 each way” costs €20. Take €10 each way at 8/1 with place terms of 1/5 of the odds for three places. If the horse wins, the win part returns €90.00 and the place part, settled at 8/5, returns €26.00: €116.00 in total from €20. If it finishes second or third, only the place part pays, €26.00. If it finishes fourth or worse, the €20 is lost. Our racing terms guide explains place terms in full.

Doubles and other multiples

In a double, the return from the first selection becomes the stake on the second. With decimal odds you simply multiply: a €10 double at 2/1 (3.00) and evens (2.00) returns €10 × 3.00 × 2.00 = €60 if both win. If either loses, the whole €10 is lost. Every extra selection makes the potential return bigger and the chance of every selection winning smaller.

What can reduce a return

The sums above assume a straightforward winning bet. In practice a return can be reduced by a Rule 4 deduction when a horse is withdrawn, by dead-heat rules when two runners tie, or by a bookmaker's maximum winnings rule. All of these are set out in the bookmaker's terms.

These examples show what happens if a bet wins. Most bets lose; never stake more than you can afford to lose.

The bookmaker’s margin in one paragraph

Add up the implied probabilities of every outcome in a market and you get more than 100%. In a two-way market priced at 10/11 on each side, each price implies 52.4%, a total of 104.8%. The 4.8 points above 100 are the bookmaker's margin, also called the overround: it is how a bookmaker builds its income into its prices. Margins vary between bookmakers, sports and markets. It is a subject of its own, and we won't go deeper into it here.

Why odds change

Prices move because the bookmaker's view changes and because of the bets it takes. Common reasons include team news and injuries, non-runners in a race, a change in the going after rain, a lot of money arriving for one outcome and, in-play, everything that happens on the pitch or the track. A price you see on Monday may be different by Saturday, in either direction. Once a bet is accepted at a price, that price normally stands, apart from adjustments the rules allow, such as Rule 4 deductions in racing or the correction of an obvious error.

Starting price or the price you take

In racing you can usually choose between taking the price on offer now (a fixed or “board” price) and the starting price (SP), which is the official price at the moment the race starts. If you take 6/1 and the horse starts at 4/1, you are settled at 6/1. If it starts at 8/1, you are settled at 6/1, unless the bookmaker has a concession on that race that pays the bigger SP; each bookmaker sets its own conditions for this. The racing terms guide covers SP in more detail.

Odds describe a price, not your chances of coming out ahead. A long price can look tempting because the possible return is large, but the price is long precisely because the outcome is unlikely. Multiples look attractive for the same reason: the return grows because the chance of every selection winning shrinks.

Understanding odds helps you know what you are agreeing to when you place a bet. It does not change the result. Betting is entertainment, not a way to earn an income. Set a deposit limit before you start, decide your stake before you look at the prices, and never chase a loss with a bigger bet.

If betting stops feeling like entertainment, free and confidential help is available in Ireland. The GamblingCare National Helpline is open 24 hours a day, 365 days a year on 1800 936 725 (gamblingcare.ie). The HSE Drugs and Alcohol Helpline is on 1800 459 459 (Monday to Friday, 9:30 to 17:30). Extern Problem Gambling offers free counselling on 089 241 5401, and Gamblers Anonymous Ireland can be reached on 01 872 1133. Our safer betting page explains limits, time-outs and self-exclusion.