Implied Probability Calculator: Odds to Win Percentage

An implied probability calculator turns a betting price into the win chance it bakes in, so −140 becomes 58.3% and +200 becomes 33.3%. Every set of odds is a probability in disguise: it tells you how often a bet must win just to break even.

Convert any American, decimal, or fractional price into that percentage with the tool below, then read on for the exact formula and a full chart.

Try It: Implied Probability Calculator

Type odds into any field and read the implied probability off the last one. It opens on even money: +100, decimal 2.00, fractional Evens, and exactly 50%.

Change any odds field and watch the percentage update, or type a probability and read back the price it implies.

The percentage in the implied probability field is your break-even win rate: the share of the time the bet has to land for the price to be fair. Everything below explains how the odds and that percentage relate.

The Implied Probability Formula

Implied probability is easiest from decimal odds, so most tools convert to decimal first. From there it is a single division.

Decimal odds invert to a probability directly:

$\text{Probability} = \frac{1}{\text{Decimal}} \times 100\%$

So decimal 2.00 implies 1 / 2.00 = 50%, and decimal 1.50 implies 1 / 1.50 = 66.7%. If your book quotes American odds, the American odds to decimal guide covers that first step on its own.

Positive American odds (underdogs) use the price plus 100 as the denominator:

$\text{Probability} = \frac{100}{\text{American} + 100} \times 100\%$

So +200 implies 100 / (200 + 100) = 33.3%, and +150 implies 100 / 250 = 40%.

Negative American odds (favorites) put the absolute value over that same value plus 100:

$\text{Probability} = \frac{\lvert \text{American} \rvert}{\lvert \text{American} \rvert + 100} \times 100\%$

So −200 implies 200 / (200 + 100) = 66.7%, and −110 implies 110 / 210 = 52.4%.

Fractional odds written as a/b imply the denominator over the sum:

$\text{Probability} = \frac{b}{a + b} \times 100\%$

So 6/1 implies 1 / (6 + 1) = 14.3%, and 1/2 implies 2 / (1 + 2) = 66.7%. All four formulas describe the same relationship, which is why converting to decimal first collapses them into one step.

Worked Example: −140 to Implied Probability

Take −140, a common favorite price. It is negative, so use the negative-odds formula: put the absolute value, 140, over 140 plus 100.

140 / (140 + 100) = 140 / 240 = 0.5833, which is 58.3%. So −140 bakes in a 58.3% win chance.

Read it back to sanity-check. At −140 you stake $140 to win $100, returning $240 total. Your stake is 140 / 240 = 58.3% of that return, which is exactly the break-even rate the price implies.

A bet at −140 that truly wins more than 58.3% of the time has positive expected value. One that wins less has negative expected value. Either way, any single result can still go against you.

Why Implied Probabilities Add Up to More Than 100%

Add the implied probabilities on both sides of a real market and you get more than 100%. A game priced −110 on each side implies 52.4% plus 52.4% = 104.8%.

Those two outcomes cannot both happen 52.4% of the time, so the extra 4.8% is not real probability. It is the bookmaker margin, called the vig or the overround.

How sportsbooks make money shows how that 4.8% overround becomes a 4.5% hold on every dollar wagered.

That gap is why implied probability is not the same as true probability. The book has padded both prices so the numbers sum above 100%. Before implied probability tells you anything about fair value, you have to strip the vig back out.

Removing it is exactly what a no vig calculator does. It scales the two implied probabilities so they sum to 100% again, which leaves the no vig fair odds behind the line.

The de-vig playbook covers the different methods for doing that and when each one fits.

From Implied Probability to Value

Implied probability is the number you actually reason about, because a price is good only relative to the real chance of the outcome. Convert the odds, strip the vig, and you have the market's fair estimate of how often a bet wins.

The edge appears when your own estimate of the true probability beats that fair number. As an illustrative example, if a fair line implies 52% but you believe the outcome hits 56% of the time, the price pays more than it should.

That gap is your expected value, and the expected value guide turns it into dollars per bet.

Turning implied probability into an edge this way is the core of positive expected value betting.

The same price can imply a different percentage at each book, which is why line shopping matters. Measuring whether the price you took beat the market's closing number is closing line value.

Converting odds to a probability tells you whether a price is fair, not whether a bet will win. Any single bet can still win or lose no matter how favorable the implied probability looks.

Implied Probability Conversion Chart

A reference for the prices you meet most often. Negative American odds are favorites (implied probability above 50%); positive are underdogs (below 50%).

Each row is a single price with no vig removed, so it is the raw break-even rate the number bakes in.

The −110 row is the one to memorize. It is the standard price on a point spread or total, and its 52.4% implied probability rather than a clean 50% is the vig showing through on a balanced market.

Frequently Asked Questions

What is implied probability in betting?

Implied probability is the win percentage a set of odds bakes in, or the break-even rate the bet must clear to be worth taking. A price of −140 implies 58.3%, meaning the bet has to win at least 58.3% of the time for the price to be fair.

It is the market's estimate of how often the outcome happens, before the bookmaker margin is removed.

How do you calculate implied probability from odds?

From decimal odds, divide 1 by the decimal and multiply by 100, so 2.00 implies 50%. For positive American odds, divide 100 by the odds plus 100, so +200 implies 33.3%.

For negative American odds, divide the absolute value by that value plus 100, so −150 implies 60%.

What does −110 mean as a probability?

−110 implies a 52.4% probability. Using the negative-odds formula, divide 110 by 210 to get 0.524.

Because a balanced market is priced −110 on both sides, each side reads 52.4% and the two sum to 104.8%. The extra 4.8% is the vig, not real probability.

Why do the two sides add up to more than 100%?

The sum above 100% is the bookmaker margin, the vig or overround. A book pads both implied probabilities so the total exceeds 100%, and that padding is its edge.

To find the true probability behind a line, strip the vig out with a no vig calculator so the two sides total 100% again.

Is implied probability the same as true probability?

No. Implied probability is the raw percentage a price bakes in, and it always includes the bookmaker margin, so both sides sum to more than 100%.

True probability is what remains after you remove the vig. The difference between the vig-free fair probability and your own estimate is where betting value comes from.

Convert Any Price Instantly

Working out one implied probability by hand is quick, and the odds converter does any single price in every format. Inside SmartStake you can skip the conversion entirely.

Set your odds format to Percent in display and behavior settings. Every price on bet cards, the Odds Screen, the Arbitrage Finder, and the Bet Tracker then shows as its implied probability.

Checking every line across every book against a fair probability is a different job.

The Positive EV tool blends sharp books, strips the vig, and lists the prices that pay more than the fair line. How it finds bets walks through the method. To score one bet yourself, the expected value calculator takes your stake, the odds, and your win probability.

Prediction markets skip the first step, since a Kalshi price in cents already is the implied probability. Prediction market betting explains how those contracts work.