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Odds, implied probability & fair prices
Decimal and fractional odds, what implied probability is, why the bookmaker's margin matters, and what the 'fair' tag means on a BetFinder price.
Updated 2026-06-07 · BetFinder team
A betting price is two things at once: what a bet pays if it wins, and a claim about how likely that is. Every odds chip on BetFinder can be read both ways, and once you can flip between them you can tell at a glance whether a price is generous, stingy or simply honest.
This guide covers the reading side: decimal and fractional odds, how a price converts into a percentage, why a bookmaker's percentages always add up to more than 100%, and what the small fair tag and the betslip's * marker are telling you. What the percentages themselves promise is covered separately in probability & confidence.
Decimal odds, with the fraction underneath
BetFinder leads with decimal odds because they are the easiest to do mental arithmetic with: the number is your total return per £1 staked, stake included. At 2.50, a winning £1 bet hands back £2.50 — your pound plus £1.50 profit. At 1.42 you get £1.42 back; at 9.00, £9.00. Bigger number, bigger payout, less likely outcome.
Because most British bettors still think in fractions, every odds chip carries a fractional odds sub-label underneath the decimal, snapped to the traditional ladder a bookmaker would quote — 2.50 shows 6/4, 1.42 shows 2/5, 9.00 shows 8/1, and 2.00 reads Evens. A fraction is profit over stake: 6/4 wins you £6 for every £4 staked. Same price, two notations.
Implied probability — the price as a chance
Divide 1 by the decimal odds and you get the implied probability — the chance the price is claiming. Odds of 2.00 imply 50%; 1.42 implies about 70%; 9.00 implies about 11%. This is the bridge between the two chips on every board row: the confidence chip says how often the pick lands, the odds chip says what you are paid when it does.
Why bookmaker prices add up to more than 100%
Here is the catch with implied probability: add it up across every outcome of a market and you always get more than 100%. Take a match priced 2.10 home, 3.50 draw, 3.80 away — that implies roughly 47.6%, 28.6% and 26.3%, which totals about 102.5%. The genuine chances of three outcomes can only ever total 100%, so the extra 2.5% is not probability at all. It is the overround— the margin built into the prices, which is how a bookmaker profits whichever outcome wins. Every price you are offered is a little shorter than the outcome's true chance deserves.
Fair odds — describing the outcome, not the price
Because of that margin, raw implied probabilities flatter every selection. So BetFinder removes the margin — the de-vigstep — before showing you anything: the inflated chances are brought back down so a market's outcomes total a true 100%. The result is fair odds and fair percentages — numbers that describe the outcome rather than the price you are being charged for it. Every percentage on the board, the match pages and the acca tools is margin-free in this sense, and calibrated against real results on top.
You can see the difference for yourself: a match page shows the pick's win probability next to Implied (with margin), the raw bookmaker-implied figure, so the gap between the price's claim and the honest chance is out in the open. More on that screen in the match pages guide.
The fair tag and the betslip's * marker
Sometimes there is no genuine bookmaker quote for a selection, but the model can still price it. Those prices are never dressed up as market odds: the odds chip swaps its fractional sub-label for a small fair tag, meaning a model-derived fair price rather than something you can necessarily get at a bookmaker. On the betslip, any leg priced this way carries a * after its odds — and if a slip contains one, the combined odds carry the * too, with a footnote spelling it out: * fair (model) price — not bookmaker-priced, so combined odds are indicative. And when a market has not formed at all, the row simply says Awaiting price — BetFinder never invents a number to fill a gap.
Why the best available price matters
The same bet is rarely the same price everywhere. One bookmaker might offer a team at 2.10 while another offers 2.25 — identical outcome, identical chance, roughly 7% more profit on a winner. BetFinder works from the best price it can see among UK-bettable books: a match page tells you Best price atwhich bookmaker, and the betslip's Compare odds at section lists where else the slip could be placed. Some of those links can be referral links — that never changes the odds you see.
Taking the best price is the closest thing betting has to free money: the probability of the outcome does not move, but your payout does, and over many bets the difference compounds. It is also where expected value comes from — when the best price beats the fair chance by enough, a small green edge tag appears, which is the subject of the value bets guide. The betslip's bookmaker tools are covered in the betslip guide. Prices move through the day, so always check the live price before betting — and only ever stake what you are comfortable losing.
Quick answers
What is the difference between decimal and fractional odds?
Notation only. Decimal odds are your total return per £1 including the stake (2.50 returns £2.50); fractional odds are profit over stake (6/4 wins £6 per £4 staked). Every odds chip shows both — decimal on top, the nearest traditional fraction underneath — so you never need to convert in your head.
Why doesn't the confidence percentage equal 1 ÷ the odds?
Because 1 ÷ odds is the price's claim, and the price includes the bookmaker's margin. BetFinder strips that margin out and calibrates the result against real outcomes, so the percentage you see is usually a touch lower than the raw implied figure — that gap is the margin you would otherwise be paying without seeing it.
What does the * on a betslip leg mean?
That leg is priced at a model-derived fair price rather than a bookmaker's quote — the same selections wear a fair tag on the board. The combined odds on such a slip are honest but indicative: check the actual price at your bookmaker before placing anything.
Does taking a better price change my chance of winning?
No — the outcome's probability is what it is regardless of who is quoting it. A better price changes only what you are paid when it lands, which is exactly why it is worth having: same risk, bigger payout, and over time that difference is most of what separates winning prices from losing ones.