Implied probability

Implied probability is the win chance a price stands for. It is also the break-even rate: a bet at that price has to win this often just to come out even over many bets. A price of −110 needs 52.4%.

The formulaCopy Anchor Link

Unitley computes it from the American price:

• A plus price: 100 ÷ (American + 100). +150 gives 100 ÷ 250 = 0.4.
• A minus price: the price without its sign ÷ (that number + 100). −150 gives 150 ÷ 250 = 0.6.

From decimal odds it is 1 ÷ decimal, which gives the same answer: 2.5 is 0.4.

The tools return the exact number. The console shows it rounded, as a percent such as 52.4%.

The vig inside itCopy Anchor Link

An implied probability includes the sportsbook's margin, the vig. You can see it when you add up both sides of one market. At −110 on each side, each side implies 52.4%, and together they come to 104.76%. A fair market would come to 100%. The extra 4.76%, an overround of 0.0476, is the book's margin.

So an implied probability overstates each side's true chance a little. Two things follow:

• calc_ev measures your edge against the implied probability, vig included. That is the price you actually bet into.
• To compare a price with a fair chance, take the vig out first. No-vig odds shows how Unitley does that.

Worked example: −110Copy Anchor Link

calc_implied_probability takes one input, americanOdds. Over the REST API:

curl -X POST https://console.unitley.com/api/v1/tools/calc_implied_probability \
  -H "Authorization: Bearer YOUR_UNITLEY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"americanOdds": -110}'

It answers:

{
  "data": {
    "americanOdds": -110,
    "decimalOdds": 1.9090909090909092,
    "impliedProbability": 0.5238095238095238
  }
}

• americanOdds is the price you sent, −110.
• decimalOdds is 1 + 100 ÷ 110 = 1.9090909090909092.
• impliedProbability is 110 ÷ 210 = 0.5238095238095238, or 52.4%.

The numbers are not rounded. Round them yourself for display, as the console does.

Over MCP, the same tool returns the same object without the data wrapper.

RelatedCopy Anchor Link

• Implied probability, the guide on the Unitley site.
• The implied probability calculator, to try a price in the browser.
• Odds formats, for converting between American and decimal odds.