On a price screen, "How do decimal odds work?" comes down to two numbers. Betting odds are a price and a forecast in one number. A short explanation covers most of it: the odds say how much a winning stake returns, and they hint at how likely the book thinks the outcome is. What does not show on the surface is the margin, which is why reading odds well means looking past the payout to the chance behind the price.
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To interpret betting odds, turn the price into two numbers: the payout and the implied chance. At decimal odds of 3.00 a stake of ten returns thirty, so the betting odds payout is thirty with twenty of it profit. The implied chance is one in three. If the event happens more often than that over many tries, the price is generous; if less often, the price is short. Every other reading of a price rests on those two numbers.
The same numbers read differently by sport. In horse racing, betting odds work across a large field, so each runner carries a long price and the chances across the field add up well past one hundred per cent. In soccer, a match has three outcomes, home, draw and away, and the draw takes a share of the probability. A moneyline in sports with no draw simply names a winner, with a favourite at short odds and an underdog at a long price.
Odds state how much a winning stake returns and hint at how likely the book rates the outcome, with its cut hidden inside.
A price on who wins outright, with the favourite at short odds and the underdog at a long price.
Only when the real chance of the outcome is higher than the chance the price implies; the size of the number alone says little.
A race has many runners, so each carries a long price, and the chances across the whole field add up well past one hundred per cent.
An odds table lines up formats side by side with implied chances, showing for instance that 1.50 means about sixty seven per cent and 11.00 about nine.
A match can end in a home win, a draw or an away win, and the draw takes its own share of the probability.