How to read betting odds: decimal odds, probability and margin

How do decimal odds work?

Decimal odds are the standard in most of Europe and Africa. Multiply your stake by the odds to get the total return, then subtract the stake to get the profit.

• £10 at 1.50 returns £15 (£5 profit).
• £10 at 2.00 returns £20 (£10 profit).
• £10 at 4.00 returns £40 (£30 profit).
• Lower odds mean the bookmaker thinks the outcome is more likely; higher odds mean less likely.

What is implied probability?

Implied probability converts a price into a percentage: 1 ÷ decimal odds. Odds of 2.00 imply 50%, 1.25 imply 80% and 5.00 imply 20%. It is the quickest way to ask “how likely does this price say the outcome is?” and compare it with your own view.

You may also see fractional odds (common in the UK) such as 6/4, which means £6 profit for every £4 staked. To convert to decimal, divide the two numbers and add 1: 6 ÷ 4 + 1 = 2.50. American odds such as +150 convert the same way: 150 ÷ 100 + 1 = 2.50. All three formats describe the same price; decimal simply makes the probability maths easiest.

Worked example: a 3-way match market

A bookmaker prices a match: home 2.00, draw 3.40, away 4.00. The implied probabilities are:

• Home: 1 ÷ 2.00 = 50.0%
• Draw: 1 ÷ 3.40 = 29.4%
• Away: 1 ÷ 4.00 = 25.0%
• Total: 104.4%

What is the bookmaker margin (overround)?

Only one of the three outcomes can happen, so the true probabilities must add up to exactly 100%. The extra 4.4% in the example above is the overround, also called the margin or vig. It is how the bookmaker builds a profit into every market: each price is a little shorter than it would be if it were fair.

To remove it, the simplest method scales each implied probability down by the total. Dividing by 1.044 gives fair probabilities of about 47.9% home, 28.2% draw and 23.9% away, which now add up to 100%. The matching fair odds are 1 ÷ 0.479 = 2.09, 3.55 and 4.18, all slightly bigger than the prices on offer.

Margins vary. Popular markets in major leagues tend to carry smaller margins than niche markets or long-odds accumulators, and the margin is not always spread evenly: bookmakers often load more of it onto longshots. That is one reason we combine prices from many bookmakers rather than relying on one. This is exactly how our predictions begin. For every match we collect odds from 20+ bookmakers, remove the margin and turn them into fair probabilities. That market view is the baseline that our research then adjusts, as explained in how we make predictions.

Value vs likelihood: what’s the difference?

A likely outcome is not automatically a good bet. Likelihood is how often something happens; value is whether the price pays enough for that likelihood. You can measure value as edge: your probability × odds − 1.

Suppose you believe the home side in our example has a 52% chance, and the odds are 2.00. The edge is 0.52 × 2.00 − 1 = +4%. Now take a heavy favourite at 1.20 that you rate 80%: 0.80 × 1.20 − 1 = −4%. The favourite is far more likely to win, but the price is too short, so over many bets like it you would expect to lose money.

Our picks show both numbers: the estimated probability, which drives the bankers and other hubs, and the odds at the time of publication. Short-priced, high-probability picks are what our 2-odds tips are built from; read the 2-odds guide to see why combining them still adds risk.

How should you use odds as a bettor?

Convert prices into probabilities before you bet, remember the margin is always there, and judge any tipster, us included, by a complete public record rather than a few wins; ours is on the results page. No bet is ever sure: only stake what you can afford to lose, and visit our responsible gambling page for help.