Rex says
The fast lane for the math you almost remember from school. Type the numbers, get the answer, move on with your day.
Try a scenario
Click to load — tweak from there.Inputs
Result
Implied probability — Side A
52.4%
Implied probability — Side B
52.4%
Market overround (vig)
4.8%
Vig-free fair probability — Side A
50.0%
Your edge vs. market (Side A)
2.6%
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter side a odds (american).
- 2Enter side b odds (american).
- 3Enter your estimated true probability for side a (%).
- 4Read your implied probability — side a on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Every posted line is a probability statement wearing a payout disguise. Odds of -150 imply a 60% win probability; +200 implies 33.3%. This calculator converts American or decimal odds into implied probability so you can compare the market's view against your own estimate before betting. It also totals both sides of a two-way market (moneyline, spread, or total) so you can see the combined percentage — anything above 100% is the sportsbook's built-in edge, commonly called the vig or juice. A market showing 52.4%/52.4% (110% total) has roughly a 10% overround, which is normal for a standard -110/-110 line. Wider or lopsided markets, like a heavy favorite at -300, often carry more hold. This tool is descriptive, not predictive: it tells you what the book is pricing, not whether that price is right. Use it alongside your own model or research to find spots where your estimated probability diverges meaningfully from the market's, which is the entire basis of a positive expected-value bet.
Worked example
Using the values the calculator loads with:
Inputs
- Side A odds (American): -110
- Side B odds (American): -110
- Your estimated true probability for Side A: 55 %
Results
- Implied probability — Side A: 52.4%
- Implied probability — Side B: 52.4%
- Market overround (vig): 4.8%
- Vig-free fair probability — Side A: 50.0%
- Your edge vs. market (Side A): 2.6%
What each field means
Inputs
- Side A odds (American)
- The side a odds (american) used in the calculation. Starts at -110 so you have a working example on load.
- Side B odds (American)
- The side b odds (american) used in the calculation. Starts at -110 so you have a working example on load.
- Your estimated true probability for Side A (%)
- The your estimated true probability for side a used in the calculation, measured in %. Starts at 55 % so you have a working example on load. Accepted range: 0–100 %.
Results
- Implied probability — Side A
- Returned as a percentage and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Implied probability — Side B
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Market overround (vig)
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Vig-free fair probability — Side A
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Your edge vs. market (Side A)
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What counts as a meaningful edge?
Sharp bettors generally look for at least a 2-3 percentage point gap between their estimated probability and the vig-free market probability before it's worth betting, because your model has to be right often enough to beat both variance and the book's hold. A 1-point edge is within typical estimation error for most casual models.
Why do both sides of a market add up to more than 100%?
That excess is the vig. A standard -110/-110 line implies 52.38% on each side, totaling 104.76%, meaning the book is taking about a 4.5% cut of the total handle regardless of outcome. Removing that overround gives you the fair, no-vig probability.
Is implied probability the same as the book's true opinion of the outcome?
Not exactly. Books also shade lines based on which side the public is betting, to balance their liability rather than to reflect pure probability. A heavily bet favorite can get shorter odds than its true win chance simply to attract action on the underdog.
Accuracy and limitations
- Results are rounded for display; the underlying calculation keeps full precision.
- Very large or very small inputs may hit floating-point limits in the browser.
- Inputs outside the accepted range are clamped rather than rejected.
Related tools
No-Vig Fair Odds Calculator
Strip the sportsbook's hold out of a two-way line to find fair odds.
Odds Format Converter (American, Decimal, Fractional)
Convert American, decimal, and fractional betting odds instantly.
Expected Value (EV) Bet Calculator
Find the dollar EV of a wager given your true win probability.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Implied Probability Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/implied-probability-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/implied-probability-calculator" target="_blank" rel="noopener">Implied Probability Calculator — RevenueLab</a> (2026).</p>
Source: [Implied Probability Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/implied-probability-calculator) (2026).