A betting price is a probability in disguise. Learn to read it, to see the bookmaker margin and to tell whether a price offers value.
Every price carries a probability. Once you can read it, you can tell what a bookmaker believes, how much margin is built in and what you need to believe for the bet to be worth taking. The maths is simple division.
Step 1: price to implied probability
Take the decimal price and divide 1 by it. If you have another format, convert it first with our guide to odds formats.
- Price 2.00: 1 / 2.00 = 50%.
- Price 1.50: 1 / 1.50 = 66.7%.
- Price 4.00: 1 / 4.00 = 25%.
Step 2: the margin
Add up the implied probabilities of every outcome in the market. Take a 1X2 market with a home win at 2.40, a draw at 3.30 and an away win at 3.00:
- Home: 1 / 2.40 = 41.7%
- Draw: 1 / 3.30 = 30.3%
- Away: 1 / 3.00 = 33.3%
The total is 105.3%. A fair market would add up to exactly 100%, so the extra 5.3% is the bookmaker's margin (also called the overround or vig). It is how the bookmaker makes a living, and it is the hurdle every bettor has to clear.
Step 3: take the margin out
To estimate what the bookmaker really thinks, divide each implied probability by the total:
- Home: 41.7 / 105.3 = about 39.6%
- Draw: 30.3 / 105.3 = about 28.8%
- Away: 33.3 / 105.3 = about 31.7%
These now add up to 100% (apart from rounding). This is a simple estimate. Bookmakers do not always spread the margin evenly, and favourites and long shots are often treated differently, but it is a fair starting point.
Step 4: what is value?
A bet has value when the real chance of the outcome is higher than the implied probability of the price. If you think the home team has a 45% chance and the price is 2.40, the bet has a positive expected return:
Expected profit per 1 staked = 0.45 x 2.40 - 1 = +0.08, or +8%.
The break-even chance for 2.40 is 41.7%. At anything above that, you are ahead over a long run, and at anything below it you are behind. A short price is not bad and a long price is not good in themselves: only the gap between your chance and the price matters.
The catch: you have to be right about the chance
The "45%" above is an opinion. If the real chance is 38%, the same bet loses money over time, however confident you feel. Betting markets are efficient on the main leagues, because a lot of money and information go into the prices, and that is why we say we do not claim to know more than the market (see how our tips are made and graded). Value is found by estimating chances carefully, checking them against results, and being honest about how often you are wrong.
How to use this
- Convert the price and check the break-even chance before you place a bet.
- Compare several bookmakers: the best available price is worth more than the pick itself over time.
- Judge a tipster or a model by return and sample size, not only by wins. See how to judge a betting record.
- Stake small and consistently, because even a real edge has long losing runs. Our bankroll management guide covers how.
18+ only. Betting can be addictive: never stake money you cannot afford to lose. Read our responsible gambling page.