Odds tell you two things: how likely the bookmaker thinks something is, and how much you get back if you are right. Irish and UK bookmakers usually show fractional odds by default, but most let you switch to decimal in the settings.
Fractional odds
Fractional odds such as 5/2 (said “five to two”) show your profit against your stake. At 5/2, a €2 stake wins €5 profit, so you get €7 back in total. At 1/2 (odds-on), a €2 stake wins €1 profit, so you get €3 back.
Decimal odds
Decimal odds such as 3.50 show your total return per €1 staked, stake included. A €10 bet at 3.50 returns €35 in total, which is €25 profit. To convert fractional to decimal, divide the fraction and add 1: 5/2 is 2.5 + 1 = 3.50.
American odds
American (moneyline) odds use a plus or minus. +250 means a €100 stake wins €250 profit. -200 means you must stake €200 to win €100 profit. They are rare with Irish bookmakers but you will meet them on US sports.
Working out the implied chance
Divide 1 by the decimal odds to get the implied probability. Odds of 4.00 imply a 25% chance (1 / 4). Add up the implied chances for every outcome in a market and you will get more than 100%. The extra is the bookmaker’s margin.
A quick reference
- Evens (1/1) is 2.00 in decimal, so a 50% implied chance.
- 2/1 is 3.00, a 33% implied chance.
- 1/4 is 1.25, an 80% implied chance.
- 10/1 is 11.00, roughly a 9% implied chance.
Short odds do not mean a bet is safe, and long odds do not mean it is good value. Value comes from odds that are bigger than the real chance, which is hard to judge. Only stake what you can afford to lose.
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