Implied Probability – How to Convert Odds to Percentages

Implied probability is the chance of an outcome that a price represents: divide 1 by the decimal odds. Odds of 2.50 imply 40%, odds of 1.543 imply 64.8%. Because every bookmaker price contains a margin, implied probabilities overstate the real chance; remove the margin first and you get the fair probability you can compare offers against.

This guide covers the formulas for every odds format, why a market adds up to more than 100%, how to get from implied to fair probability, and how to use the number in practice. The worked example uses a real Pinnacle price.

Definition. Implied probability is the probability that a set of odds assumes, including the bookmaker's margin. For decimal odds it is 1 ÷ odds. The fair (no-vig) probability is the implied probability after the margin has been removed from the whole market.

What does implied probability tell you?

It turns a price into a percentage, so you can compare it with any other price or with your own estimate on the same scale. A price is a payout; a probability is a claim about how often the outcome happens. Converting is the first step in every value-betting calculation.

It tells you three things:

• The bookmaker's view plus margin. 1.91 implies 52.4%. The bookmaker thinks the outcome happens a bit less often than that; the gap is its cut.
• Your break-even rate. At 1.91 you need to win more than 52.4% of the time to come out ahead over many bets. At 3.00 you need more than 33.3%.
• The size of a move. A price going from 1.826 to 1.543 is a 15.5% drop in odds and a rise from 54.8% to 64.8% in implied probability: 10 percentage points. Points are easier to compare across prices than percentage drops. See how to read odds movement.

How do you convert odds to implied probability?

Use the formula for the format you have. The odds converter does it for any price.

Multiply by 100 to read it as a percentage. If you are unsure how each format pays out, start with how to read betting odds.

How do you convert a probability back to odds?

Invert it. Decimal odds = 1 ÷ probability. A 25% chance is 4.00; 60% is 1.667; 31.9% is 3.135.

For American odds: if the probability is under 50%, odds = (100 ÷ p) − 100, so 25% = +300. If it is over 50%, odds = −100 × p ÷ (1 − p), so 60% = −150.

This is how a fair price is quoted. You estimate or derive a probability, then turn it into the odds that would be break-even.

Why do implied probabilities add up to more than 100%?

Because the bookmaker builds in a margin. In a fair market, the probabilities of all outcomes add to exactly 100%, since one of them must happen. Bookmakers shorten every price a little, so the total goes above 100%. The excess is the overround.

A tennis match priced 1.30 and 3.60:

• 1 ÷ 1.30 = 76.9%
• 1 ÷ 3.60 = 27.8%
• Total: 104.7%, a margin of 4.7%

Pinnacle's help centre says its markets average 102% (a 2% margin), against an industry average of around 106% (Pinnacle Help Center, "What is a betting margin?", updated 25/03/2026, read 28/10/2026). Lower margins mean implied probabilities closer to the fair ones. The full explanation is in overround, vig and margin explained, and the margin calculator works it out for any market.

How do you get the true (fair) probability?

Remove the margin from the whole market. This is called devigging. You need every outcome's price, not just the one you want to bet.

Multiplicative (normalisation). Divide each implied probability by the total. For 1.30 / 3.60: 76.9% ÷ 104.7% = 73.5% and 27.8% ÷ 104.7% = 26.5%. Fair odds 1.361 and 3.769.

Power. Raise each implied probability to the same power so they add to 100%. It takes more of the margin from the longshot, in line with the favourite-longshot bias. It is the default in Pinnacle Terminal. For 1.30 / 3.60 it gives 75.2% and 24.8%, fair odds 1.330 and 4.028.

The two methods agree on favourites and differ most on longshots. Additive and Shin are other common choices. The devig methods guide compares them with worked numbers, and the devig calculator runs all of them.

A fair probability is still an estimate. It is the market's best view at that moment, not a fact about the match. It is useful because Pinnacle runs low margins, takes large bets and accepts winners, so its price is the sharpest single reference most bettors have; see why Pinnacle is the sharp reference price.

Real example: implied vs fair probability on a Pinnacle drop

From Pinnacle Terminal on 28 October 2026, around 09:37 Madrid time (CET). ITF Women Poitiers, Manon Leonard v Amandine Hesse. Market: games handicap, Leonard −3.5.

• Pinnacle's price dropped from 1.826 to 1.543, labelled Limit-backed (the price fell and Pinnacle raised the limit).
• Implied probability before: 1 ÷ 1.826 = 54.8%. After: 1 ÷ 1.543 = 64.8%. A move of 10 points.
• Fair price after removing the margin (power method): 1.631, a fair probability of 61.3%.
• The 3.5-point gap between 64.8% and 61.3% is the share of Pinnacle's margin sitting on this side.

What it means in practice: a bookmaker still offering 1.75 on Leonard −3.5 implies 57.1%, below the fair 61.3%. That price was longer than fair. The expected value against the fair price is 1.75 × 0.613 − 1 = +7.3%. A price of 1.60 implies 62.5%, above fair: no value. (The 1.75 and 1.60 are illustrative, not quotes from a real bookmaker.)

The same comparison works for any bet: if the bookmaker's implied probability is lower than the fair probability, the price is value. The EV calculator does the arithmetic; what is a value bet covers the method.

Common mistakes with implied probability

• Treating it as the real chance. It includes the margin. On a 2-way market at 1.91 / 1.91, each side implies 52.4%, but neither is more likely than 50%.
• Devigging one side alone. You need every outcome in the market to remove the margin.
• Mixing markets. A 1X2 price and a draw-no-bet price for the same team are different bets with different probabilities.
• Comparing percentage drops across prices. A 10% drop at 1.50 and at 5.00 are very different moves in points.
• Forgetting exchange commission. At 2% commission, a 2.50 back bet pays like 2.47 (1 + 1.50 × 0.98), an implied 40.5%, not 40.0%.

How Pinnacle Terminal handles this

Pinnacle Terminal shows Pinnacle's price on each line with the fair price (NVP) beside it, calculated with power devig by default; multiplicative, additive and Shin are also available, plus a worst-case figure. So the implied-to-fair step is already done when a move appears. Every pre-match move is graded 0–10 and labelled (Big move, Sharp drop, Limit-backed, Downtrend, Rebound, Standard), so you instantly see which ones matter; live in-play drops are shown as they happen and filtered, without a grade. The terminal does not accept bets and is not affiliated with Pinnacle. More on the Pinnacle dropping odds page.

FAQ

What is the formula for implied probability?

For decimal odds, implied probability = 1 ÷ odds. For fractional a/b, it is b ÷ (a + b). For American plus odds, 100 ÷ (odds + 100); for minus odds, |odds| ÷ (|odds| + 100).

What is the implied probability of −110?

110 ÷ 210 = 52.4%. Two sides at −110 add up to 104.8%, so each side's fair probability is 50%.

Is implied probability the same as the real probability?

No. It includes the bookmaker's margin, so it is higher than the fair probability. Removing the margin across the whole market gives the fair (no-vig) probability, which is still an estimate.

How do I use implied probability to find value?

Compare the bookmaker's implied probability with a fair probability, for example Pinnacle's devigged price. If the bookmaker implies less than the fair probability, its odds are longer than fair and the bet has positive expected value against that estimate.

Why do the probabilities in a market add up to more than 100%?

Because each price is shortened by the bookmaker's margin. The total minus 100% is the margin, also called overround or vig.

Try it

See Pinnacle's prices with the fair probability already calculated, every pre-match move graded 0–10 and live in-play drops filtered: start the Pinnacle Terminal 7-day free trial. Nothing is charged before day 8.

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