Implied probability explained

The formula: decimal odds to a percentage

For decimal odds, the maths is a single division:

- Implied probability = 1 ÷ decimal odds × 100

Run the common prices through it:

• 1.20 → 1 ÷ 1.20 = 83.3%
• 1.50 → 66.7%
• 2.00 → 50.0%
• 2.50 → 40.0%
• 3.00 → 33.3%
• 5.00 → 20.0%
• 10.00 → 10.0%

Short prices carry a high implied probability; long prices carry a low one. A 1.20 favourite is the market saying "this happens roughly 83 times in 100". That is the number to hold in your head, not the raw decimal.

If you bet in fractions, convert to decimal first: 5/2 = (5 ÷ 2) + 1 = 3.50, which is 28.6%. Evens (1/1) = 2.00 = 50%.

Worked example: a Premier League match

Take a typical Premier League match priced up in the 1X2 (match result) market:

• Home win: 1.90
• Draw: 3.60
• Away win: 4.20

Convert each price:

• Home 1.90 → 1 ÷ 1.90 = 52.6%
• Draw 3.60 → 27.8%
• Away 4.20 → 23.8%

Add them up: 52.6 + 27.8 + 23.8 = 104.2%.

In a fair market with no margin the three probabilities would total exactly 100%. The extra 4.2% is the bookmaker's overround — the cushion built into the prices. That is what stands between the posted odds and true probability.

To strip it out and estimate the "true" implied chance, divide each figure by the total:

• Home: 52.6 ÷ 104.2 = 50.5%
• Draw: 27.8 ÷ 104.2 = 26.7%
• Away: 23.8 ÷ 104.2 = 22.8%

Now they sum to 100%. Those adjusted numbers are a cleaner read of what the market actually thinks, with the margin removed.

Overround: why the percentages beat 100%

The amount by which implied probabilities exceed 100% is the overround (or vig). It is the single most useful thing implied probability reveals, because it tells you how much room the price has been shaved by.

A tighter overround means prices sit closer to true probability, so more of any theoretical edge stays with you. On our sampled markets across UK bookmakers the average margins spread noticeably:

• Betfair: 4.6% average margin (sampled 278 markets)
• BetMGM: 5.2%
• Coral: 5.7%
• Ladbrokes: 5.9%
• Unibet: 5.9%
• Sky Bet: 6.5%
• Betway: 6.8%
• Paddy Power: 7.1%
• bet365: 7.4%
• BetVictor: 7.7%
• BoyleSports: 7.8%

Read those as factual margin averages from the sample, not a promise about any individual price. A 4.6% book and a 7.8% book on the same three-way football market are the difference between implied probabilities totalling around 104.6% and around 107.8%. Over a season of coupons, that gap compounds. It is also why shopping the same fixture across several books matters — see our betting odds United Kingdom pages for live prices.

Using implied probability to spot value

Value exists when your own estimated probability is higher than the market's implied probability. The rule:

• If your estimate > the price's implied probability → potential value bet.
• If your estimate < the implied probability → the price is too short.

Example. Say you rate an ATP Tour player at 60% to win a match. The bookmaker prices him at 1.80, which is an implied probability of 55.6%. Your 60% is above 55.6%, so on your read there is an edge. Flip it: if he were priced at 1.60 (62.5% implied), your 60% now sits below the market and there is no value.

The honest catch is that your estimate has to be good. The market's implied probability already bakes in team news, form and money flow. Implied probability doesn't hand you winners — it gives you a fair yardstick to test your own opinion against the posted price. Track how markets shift with our market movers feed and sharpen estimates using predictions.

Quick reference and margin per selection

Keep this table for fast conversions at match time:

• 1.10 → 90.9%
• 1.25 → 80.0%
• 1.40 → 71.4%
• 1.67 → 59.9%
• 1.80 → 55.6%
• 2.20 → 45.5%
• 3.50 → 28.6%
• 6.00 → 16.7%
• 11.00 → 9.1%

One practical point on multi-runner markets like horse racing or an outright: the more selections in the book, the larger the total overround tends to be, because a margin sits on every runner. A 12-runner handicap can total well over 120% once every price is converted. Divide each runner's implied probability by the book total to get the margin-free read, exactly as in the football example above. Our betting tools and horse racing odds pages help you compare those prices across bookmakers before you commit.