Implied probability calculator.
Implied probability is the win chance that a set of betting odds represents. Enter any price and this free calculator converts it to a percentage, then lets you compare it with your own estimate to see whether the bet holds value. It works in decimal or American odds, and it will also turn a probability straight back into odds.
Odds to win chance
LiveImplied probability
60.00%
the odds imply this win chance
Implied probability is also your break-even win rate: you must win at least this often just to break even. If your own estimate is higher, the bet has value. Calculations run in your browser; nothing is stored. For entertainment, not betting advice.
The short answer
What is implied probability?
Implied probability is the win chance that a set of betting odds represents, expressed as a percentage. It is found by converting the odds into a probability, and it tells you how likely the bookmaker’s price suggests an outcome is. It is also your break-even point: the share of the time a bet must win simply to avoid losing money.
How to use this calculator
Pick your odds format and type in the price. The calculator instantly shows the implied probability as a percentage. If you also enter your own estimate of the win chance, it compares the two and tells you whether the bet has value: your edge is the gap between your estimate and the implied probability, and a positive gap means the odds are paying more than your read suggests.
Lower down, a second converter does the reverse, turning any probability you have in mind straight back into fair odds.
The formulas
One step per
odds format.
Every format converts to a probability with a single line of arithmetic.
# Decimal odds
implied = 1 / decimal odds
# American, negative (e.g. -150)
implied = |odds| / (|odds| + 100)
# American, positive (e.g. +120)
implied = 100 / (odds + 100)
# Fractional odds (e.g. 5/2)
implied = denom / (numer + denom)
# Reverse: probability to fair odds
fair odds = 1 / probabilityThe other direction
Turn a probability into odds.
Have a win chance in mind? Enter it here to see the fair odds that match it, the price at which the bet would be break-even.
Fair decimal odds
1.82
Fair American odds
-122
A 55% chance corresponds to fair odds of 1.82, or -122 in American. If a bookmaker offers you anything longer than that on a 55% shot, say 2.00 or +110, you are getting paid more than the true chance, which is exactly what a value bet looks like.
The whole point
Implied probability and value.
Converting odds to a percentage is not just a maths exercise. It is how you decide whether a bet is worth making.
Every bet comes down to one comparison: the chance the odds imply against the chance you actually believe in. If you think a team wins 60% of the time but the odds only imply 50%, the bookmaker is paying you as though the outcome is less likely than it is. That gap is positive expected value, the foundation of every winning betting strategy.
Turn it around and the same logic warns you off bad bets. If the odds imply 60% but your honest estimate is 50%, you are being asked to accept a price that undervalues the risk, and over time bets like that lose. Implied probability gives you a single, comparable number to hold your own judgement against. Without it, you are guessing whether a price is generous; with it, you can measure exactly how generous, or how mean, it really is. The value check built into this calculator does that comparison for you the moment you enter an estimate.
A quirk worth knowing
Why odds add up over 100%.
Add the implied probabilities of every outcome in a market and you get more than 100%. That surplus is the bookmaker’s margin.
In a fair, true market the probabilities of all outcomes would sum to exactly 100%. They never do at a bookmaker. Take a coin-flip market priced -110 on both sides: each side implies 52.38%, and together they add to 104.76%. That extra 4.76% is the vig, the commission baked into the odds, and it is the reason implied probability is always a little higher than the outcome’s true chance.
This matters when you read a single price. The implied probability you get from one set of odds includes a slice of that margin, so it slightly overstates the real likelihood. Sharp bettors strip the margin out, by removing the vig across both sides of a market, to find the fair probability before judging value. For a quick read, though, the raw implied probability is close enough, as long as you remember it is tilted in the book’s favour, not yours.
For reference
Common odds and their chance.
A few prices worth memorising, so you can sense-check the calculator at a glance.
Evens, written 2.00 or +100, is a straight 50%. Odds of 1.50, which is 1/2 or -200, imply 66.7%, while 3.00, which is 2/1 or +200, imply 33.3%. The standard American line of -110 sits at 52.4%, just over a coin flip, and a heavy favourite at 1.25, which is 1/4 or -400, implies 80%.
At the longshot end the numbers fall away fast: 11.00, or 10/1, is just 9.1%, and 21.00, or 20/1, only 4.8%. A handy shortcut for decimal odds is that the implied probability is simply 1 divided by the price, so 4.00 is a quarter, or 25%, and 5.00 is a fifth, or 20%. Keep a few of these in your head and you will spot a mispriced line without reaching for a calculator at all.
A hidden tilt
Favourite-longshot bias.
Implied probabilities are not evenly accurate. Longshots tend to be overbet, and their odds overstate their real chance.
Studies of betting markets going back decades find a consistent pattern: bettors overvalue long shots and undervalue favourites. The dream of a big payout makes people pile onto outsiders, so bookmakers can offer those runners worse value than their true chance, while shortening the value gap on favourites to attract money. The upshot is that the implied probability on a longshot usually overstates how often it really wins.
For you, that means a longshot’s implied probability is a ceiling, not a fair estimate, and favourites are more often where genuine value hides. It does not make every favourite a good bet, but it is a useful lean: when the implied probability of an outsider looks tempting, remember the market is structured to make those prices worse than they appear. Treat the percentage as the book’s optimistic version of the chance, then apply your own, usually more sober, estimate.
Worked through
Two numbers, one decision.
Every value judgement comes down to the implied chance against your own. Here it is in practice.
Take the calculator’s default of -150. The negative-odds formula is the odds over the odds plus 100, so 150 divided by 250, which is 60%. The price is saying this outcome wins three times in five. Now suppose you have studied the matchup and think it really wins 65% of the time. Your estimate beats the implied figure by five points, so the bet has value, and that is exactly the verdict the calculator returns.
Flip it round to see the warning. A +250 longshot implies 100 divided by 350, about 28.6%. If your honest read is only 20%, the price looks tempting but is poor value, and backing it would lose over the long run. Nothing else changed, just the two percentages: the chance the odds imply, and the chance you actually believe in. Get into the habit of comparing those two before every bet and you are already ahead of most punters.
The next step
From probability to expected value.
Implied probability tells you the break-even line. Expected value tells you how far past it a bet sits.
Expected value, or EV, is the average result of a bet repeated many times. If your true win chance is p and the decimal odds are d, the expected value of a 1 stake is p times (d minus 1), minus (1 minus p). A positive answer means the bet makes money in the long run; a negative one means it bleeds.
Say you back a 2.50 shot you rate at 45%. The maths is 0.45 times 1.5, which is 0.675, minus 0.55, leaving plus 0.125, or 12.5% profit per unit staked. The implied probability of 2.50 is 40%, and your 45% read is exactly where that edge comes from. This is why implied probability is the starting point for everything: it sets the break-even percentage, and the moment your estimate clears it, the bet carries positive expected value. The bigger the gap, the bigger the edge.
Before you bet
An honest word.
Implied probability is one of the most useful numbers in betting, but it is only the bookmaker’s view of the chance, complete with their margin. Turning it into a profit still depends on the hard part: estimating the true probability better than the market does. The calculator makes the comparison instant, it does not make your estimate correct. Be honest with the win chances you enter, because fooling yourself there just produces value bets that are not really there.
Only ever stake money you can afford to lose, and if betting stops being fun or starts to feel out of control, free confidential help is available at BeGambleAware.org.
Questions
Implied probability questions.
What is implied probability in betting?
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Implied probability is the win chance that a set of odds represents, written as a percentage. It is found by converting the odds into a probability and tells you how likely the bookmaker’s price suggests an outcome is. It also doubles as your break-even rate, the share of the time a bet must win to avoid a loss.
How do you convert odds to implied probability?
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For decimal odds, divide 1 by the price. For negative American odds, divide the odds by the odds plus 100. For positive American odds, divide 100 by the odds plus 100. For fractional odds, divide the denominator by the sum of both numbers. Multiply by 100 for a percentage.
What is a value bet?
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A value bet is one where your estimated chance of winning is higher than the probability the odds imply. If you believe an outcome is 60% likely but the odds only imply 50%, the price pays more than the true risk, giving you positive expected value. Over many such bets, that edge is how bettors profit.
Why do implied probabilities add up to more than 100%?
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Because of the vig, the bookmaker’s margin. In a fair market the outcomes would sum to 100%, but odds are shaded so they total more, often 104% to 110%. A -110/-110 market adds to 104.76%, and that extra 4.76% is the book’s built-in profit, which makes each implied probability slightly higher than the true chance.
How do you convert a probability back into odds?
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Divide 1 by the probability expressed as a decimal. A 55% chance is 1 divided by 0.55, which is 1.82 in decimal odds, or -122 in American. Those are the fair odds for that probability, the break-even price. The reverse converter on this page does it for you instantly.
What does implied probability tell you?
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It tells you how likely the odds say an outcome is, and therefore how often you would need that bet to win just to break even. Comparing it with your own estimate of the chance is how you judge whether a price is good value or poor, making it one of the most practical numbers in betting.
Is implied probability the real chance of winning?
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Not quite. Implied probability includes the bookmaker’s margin, so it slightly overstates the true chance of an outcome. To get closer to the real probability you remove the vig across all outcomes of a market. The raw figure is a good quick guide, but remember it is tilted in the book’s favour.
What is the implied probability of even odds?
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Exactly 50%. Even odds, written 2.00 in decimal or +100 in American, mean you double your money on a win, which corresponds to a one-in-two chance. It is the cleanest example of the conversion: a fair coin flip priced at evens implies a 50% probability for each side.
How is implied probability used to find value?
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You compare it with your own estimate of the chance. If your estimate is higher than the implied probability, the odds are paying more than the outcome deserves and the bet has value. If it is lower, the price is poor. Doing this consistently, on many bets, is the core of a value-betting approach.
What is the difference between implied and true probability?
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Implied probability is what the odds suggest, including the bookmaker’s margin. True probability is the actual chance of the outcome, which no one knows for certain. Betting profitably means estimating the true probability more accurately than the market and backing the cases where it beats the implied figure.
How accurate is implied probability?
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It accurately reflects what the odds say, but not necessarily the true chance, because it includes the bookmaker’s margin and any market biases. It is a reasonable guide in efficient, heavily bet markets and less reliable in niche ones. Treat it as the market’s opinion of the chance, not a guaranteed fact.
What odds imply a 50% chance?
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Evens: 2.00 in decimal, +100 in American, or 1/1 fractional. Any price shorter than 2.00 implies more than 50%, and any price longer implies less. Evens is the natural dividing line between a favourite and an underdog, and the cleanest example of the conversion.
Can implied probability be over 100% for one bet?
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No. A single outcome’s implied probability is always between 0 and 100%. It is only when you add up every outcome in a market that the total tops 100%, and that surplus is the bookmaker’s vig, not the chance of any single result.
Does implied probability include the vig?
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Yes. The implied probability from a single price has the bookmaker’s margin baked in, which is why it slightly overstates the true chance. Removing the vig across all outcomes of a market gives a fairer probability, but for a quick read the raw figure is still useful.
About the developer
Jean Borg
Jean builds and maintains every calculator on freecalculators.pro from Malta, with a focus on tools that are fast, free and show their working. This implied probability calculator converts odds to a win percentage, checks for value and reverses the maths, all verified for accuracy. It is provided for education, not as betting advice. Please bet responsibly. Page last updated June 2026.