{
  "slug": "implied-probability-calculator",
  "title": "Implied Probability Calculator",
  "heading": "Implied Probability Calculator",
  "category": "math",
  "url": "https://www.revenuelab.fyi/toolbox/implied-probability-calculator",
  "summary": "See the win probability a betting line is actually pricing in.",
  "description": "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.",
  "formula": "Implied probability = 100 ÷ (American + 100) for positive odds, or |American| ÷ (|American| + 100) for negative odds. Overround = sum of both sides' implied probabilities − 100%.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=implied-probability-calculator",
  "inputs": [
    {
      "id": "sideA",
      "label": "Side A odds (American)",
      "kind": "number",
      "hint": null,
      "default": -110,
      "unit": null,
      "min": null,
      "max": null
    },
    {
      "id": "sideB",
      "label": "Side B odds (American)",
      "kind": "number",
      "hint": null,
      "default": -110,
      "unit": null,
      "min": null,
      "max": null
    },
    {
      "id": "yourProb",
      "label": "Your estimated true probability for Side A",
      "kind": "number",
      "hint": null,
      "default": 55,
      "unit": "%",
      "min": 0,
      "max": 100
    }
  ],
  "outputs": [
    {
      "id": "impliedA",
      "label": "Implied probability — Side A",
      "format": "percent",
      "hint": null,
      "primary": true
    },
    {
      "id": "impliedB",
      "label": "Implied probability — Side B",
      "format": "percent",
      "hint": null,
      "primary": false
    },
    {
      "id": "overround",
      "label": "Market overround (vig)",
      "format": "percent",
      "hint": null,
      "primary": false
    },
    {
      "id": "fairA",
      "label": "Vig-free fair probability — Side A",
      "format": "percent",
      "hint": null,
      "primary": false
    },
    {
      "id": "edge",
      "label": "Your edge vs. market (Side A)",
      "format": "percent",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Side A odds (American): -110",
      "Side B odds (American): -110",
      "Your estimated true probability for Side A: 55 %"
    ],
    "outputs": [
      "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%"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter side a odds (american).",
      "Enter side b odds (american).",
      "Enter your estimated true probability for side a (%).",
      "Read your implied probability — side a on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "sideA": -65,
        "sideB": -65,
        "yourProb": 33
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "sideA": -110,
        "sideB": -110,
        "yourProb": 55
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "sideA": -175,
        "sideB": -175,
        "yourProb": 88
      }
    }
  ],
  "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."
  ],
  "faq": [
    {
      "q": "What counts as a meaningful edge?",
      "a": "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."
    },
    {
      "q": "Why do both sides of a market add up to more than 100%?",
      "a": "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."
    },
    {
      "q": "Is implied probability the same as the book's true opinion of the outcome?",
      "a": "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."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/no-vig-fair-odds",
    "https://www.revenuelab.fyi/toolbox/odds-format-converter",
    "https://www.revenuelab.fyi/toolbox/expected-value-bet-calculator"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Implied Probability Calculator (https://www.revenuelab.fyi/toolbox/implied-probability-calculator)"
}