Fair odds explained — and how to use them
Fair odds are the price a bet would have if nobody took a cut: the odds at which you'd break even over thousands of bets. Once you know the fair price, every other price becomes easy to judge — bigger is value, smaller is margin.
From odds to probability, and back
Every price hides a probability. For decimal odds, divide 1 by the price:
| Decimal odds | Fractional | Implied chance |
|---|---|---|
| 1.50 | 1/2 | 66.7% |
| 2.00 | Evens | 50% |
| 3.00 | 2/1 | 33.3% |
| 5.00 | 4/1 | 20% |
It works the other way too: if something has a 25% chance, its fair odds are 1 ÷ 0.25 = 4.00. Our odds converter does it for any format.
Where the margin hides
Add up the implied chances for every outcome in a bookmaker's market and you'll get more than 100%. Take a football match priced home 2.10, draw 3.40, away 3.60:
47.6% + 29.4% + 27.8% = 104.8%
The 4.8% above 100 is the bookmaker's margin, sometimes called the overround. Take it out — scale each chance down so they add to 100% — and you're left with fair odds of roughly 2.20, 3.56 and 3.77. Our margin calculator does this for any market.
Where a fair price really comes from
Stripping the margin out of one bookmaker's prices only tells you what that bookmaker thinks. Better sources of a fair price:
- Sharp bookmakers and betting exchanges. Their prices are moved by the best-informed money, so with the margin removed they're the closest thing to a "true" price. Our value-bet alerts compare soft UK bookmakers against exactly this kind of sharp line.
- A model. Where no sharp market exists — bet builders, for instance — you need your own estimate. Our bet builder model prices every slip from each player's recent data. How it works →
Using fair odds to spot value
Value is simply a price bigger than the fair price. If the fair odds are 3.10 and a bookmaker offers 3.40, you're getting about 10% more than the bet is worth. It doesn't mean the bet will win — at 3.40 it still loses more often than not — but over hundreds of bets like it, you'd expect to come out ahead. Our value bet calculator shows the edge and the expected profit for any pair of prices.
The same logic is how we'd judge a bet builder: every slip we post comes with its fair odds, so you can see in seconds whether your bookmaker's price is worth taking.
Fair odds and arbitrage
When two bookmakers disagree so much that their best prices add up to less than 100%, you have an arbitrage: back every outcome with the right stakes and you profit whatever happens. It's the same sum, read the other way round. What is arbitrage betting? →
Get the picks before kick-off
A new feature: up to three data-picked bet builder slips a day, with fair odds, free in our Telegram channel 15–40 minutes before kick-off. Not guaranteed — subscribers get every slip.
📱 Join the Free ChannelQuestions
What are fair odds in betting?
The odds a bet would have with no bookmaker margin: 1 divided by the true probability of the outcome. A 25% chance has fair odds of 4.00. At fair odds you'd break even over time.
How do I calculate implied probability?
Divide 1 by the decimal odds and multiply by 100. Odds of 2.50 imply a 40% chance.
What is a value bet?
A bet where the bookmaker's odds are higher than the fair odds — the price is bigger than the outcome's real chance justifies.
Keep reading
Bet builders are a new feature and are not guaranteed: unlike our arbs, most slips lose, and our record shows it. Bet only what you can afford to lose. 18+. BeGambleAware.org