NinetyHow football win probability works
A win probability is the chance, as a percentage, that a team wins a match. It can come from bookmaker odds, a prediction market price or a statistical model. They all try to answer the same question, and when they agree you can trust the number a bit more.
Turning odds into a percentage
Decimal odds of 2.00 mean a 50% chance (1 ÷ 2.00). Odds of 4.00 mean 25%, and 1.50 means about 67%. This is the implied probability.
If you do that for home win, draw and away win you will find the three add up to more than 100%, often 104% to 108%. The extra is the bookmaker’s margin, sometimes called the overround. To get a fair probability, divide each implied probability by the total so they add to exactly 100%.
Worked example
Home 2.10, draw 3.40, away 3.50. Implied: 47.6%, 29.4%, 28.6%, which totals 105.6%. Divide each by 1.056 and you get 45.1%, 27.8% and 27.1%. That is the market’s best estimate with the margin removed.
Prediction markets
On a prediction market such as Polymarket or Kalshi, a share that pays out if a team wins trades at a price between 0 and 100 cents. A price of 45 cents is read as a 45% chance. The prices come from what traders are willing to pay, so they move quickly with news such as a line-up or an injury. Ninety shows these prices as win chances, with no betting links.
Statistical models
Want to try the conversion yourself? The odds to probability calculator does it for any three prices and strips the margin.
A model estimates each team’s attacking and defensive strength from past results and shot quality, adds home advantage and the likely line-ups, and simulates the match. Ninety’s own model is called 90Machine, and we publish its record against the bookmakers and prediction markets on the track record page.
What a percentage does not mean
A 70% favourite loses three times in ten. A single result never proves a forecast right or wrong; what matters is whether, across hundreds of matches, the 70% calls win about 70% of the time. That is called calibration.
Questions
Why do the three probabilities add up to more than 100%?
Bookmaker odds include a margin. Divide each implied probability by the total to remove it.
Are prediction market prices better than bookmaker odds?
Both are good. Sharp bookmakers such as Pinnacle are usually the hardest to beat. Ninety’s track record page compares them match by match.
How do I turn a percentage into odds?
Divide 1 by the probability. A 40% chance is 1 ÷ 0.40 = 2.50 in decimal odds.
Does Ninety encourage betting?
No. Ninety has no betting links, no bookmaker partnerships and no odds to place bets. It shows win chances as information.
Last updated Sunday 1 November 2026. Written by the Ninety team; spot a mistake? [email protected].