Betting Odds Explained
Betting odds are a price for probability. Every set of odds, in any format, answers the same two questions: how likely does the bookmaker rate this outcome, and how much will you be paid if it happens? Once you can read both answers at a glance, most of betting's apparent complexity disappears.
The three formats
Decimal odds state your total return per unit staked. At 2.50, a £10 bet returns £25: your stake back plus £15 profit. They are the easiest format to compare and the one used across this site.
Fractional odds state profit relative to stake. 6/4 means £6 profit for every £4 staked, so a £10 bet returns £25 — the same price as decimal 2.50. Convert any fraction to decimal by dividing and adding one: 6 ÷ 4 + 1 = 2.50.
American odds quote against 100 units: +150 means 100 wins 150 (decimal 2.50 again), while -200 means you must stake 200 to win 100 (decimal 1.50). You will meet them on US-facing sites and rarely elsewhere.
The odds converter translates between all three instantly, with the fourth and most important number alongside.
Implied probability, the number that matters
Divide 100 by the decimal odds and you get the probability at which the price breaks even. Odds of 2.00 imply 50%; 1.25 implies 80%; 5.00 implies 20%. This single conversion is the most useful habit in betting, because it turns every price into a claim you can argue with. A bookmaker offering 1.60 on a home win is asserting the side wins about 62.5% of the time. Your entire betting decision reduces to whether you have grounds to say the true figure is higher.
Where the margin hides
Add up the implied probabilities across a whole market and the total always exceeds 100%. A typical match might price home, draw and away at implied probabilities summing to 105 or 106. That excess is the overround, the bookmaker's built-in margin, and it means the odds are collectively a little meaner than the true probabilities everywhere. Margins vary by market and operator: big-league match odds might carry 4 to 5 percent, while obscure markets and multiples run far higher. It is why comparing prices across bookmakers is worth real money, and why a bet must beat not just the true probability but the margin on top.
A worked example
Arsenal are 1.53 at one bookmaker and 1.60 at another for the same match. Implied probabilities: 65.4% against 62.5%. If your estimate of Arsenal's true chance is 64% — say, from the model — the first price is against you and the second is marginally with you. Identical opinion, opposite verdicts, decided entirely by price. That is betting in one example.
Odds also move, and the direction of movement is information: a price shortening from 1.60 to 1.50 means money and, usually, informed money agrees with the outcome. Whether you should care depends on whether your reasons were already in the price.
Every selection on this site shows its odds and the model's probability side by side, with the gap between them stated as the edge. The value betting guide explains why that gap, and nothing else, is what pays over time.