No-vig odds

A sportsbook's prices on one market add up to more than 100%. The extra is the book's margin, the vig. A no-vig price, or fair price, takes that margin out and leaves each side's chance as if the book took nothing.

OverroundCopy Anchor Link

The overround is the margin in one number: the implied chances of every outcome added up, minus 1.

See Implied probability for how each chance comes from its price.

Taking the margin outCopy Anchor Link

Unitley has two methods. Both return fair chances that add up to exactly 1, and a fair decimal price of 1 ÷ the fair chance for each outcome.

MultiplicativeCopy Anchor Link

This is the default. Each implied chance is divided by the total of all of them, so every side gives back the same share of the margin.

For −150 / +130 the total is 1.0347826…, so:

PowerCopy Anchor Link

Each implied chance is raised to the one power that makes them add up to 1. This takes more of the margin from the longshot and less from the favorite. For the same −150 / +130 market it gives about 58.40% and 41.60%, or fair prices of −140 and +140.

A market with no margin, where the chances add up to 100% or less, comes out the same under both methods.

Worked example: −110 both waysCopy Anchor Link

calc_no_vig_odds takes prices, every outcome's American price in one market, and an optional method of multiplicative or power. Send 2 to 20 prices: two for a moneyline, spread or total.

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

{
  "data": {
    "method": "multiplicative",
    "overround": 0.04761904761904767,
    "outcomes": [
      {
        "americanOdds": -110,
        "impliedProbability": 0.5238095238095238,
        "fairProbability": 0.5,
        "fairDecimalOdds": 2,
        "fairAmericanOdds": 100
      },
      {
        "americanOdds": -110,
        "impliedProbability": 0.5238095238095238,
        "fairProbability": 0.5,
        "fairDecimalOdds": 2,
        "fairAmericanOdds": 100
      }
    ]
  }
}

• overround is 0.04761904761904767, a 4.76% margin.
• Each outcome keeps its impliedProbability of 0.5238095238095238.
• Each fairProbability is 0.5, so each fairDecimalOdds is 2 and each fairAmericanOdds is 100, even money.

The outcomes come back in the order you sent them. fairAmericanOdds is rounded to a whole number. The other values are exact.

The consensus in get_game_oddsCopy Anchor Link

get_game_odds shows FanDuel's line for each market, and gives each outcome a fairProbability and fairAmericanOdds. These are a no-vig consensus across the books Unitley tracks, worked out like this:

1. A book joins the consensus only if it prices exactly FanDuel's outcomes at FanDuel's lines. A book hanging −3.5 where FanDuel hangs −3 is offering a different bet, so it is left out.
2. Each of those books has its margin taken out with the multiplicative method.
3. The fair chances are averaged across the books, outcome by outcome.

consensusBooks says how many books went in, FanDuel included. A value of 1 means FanDuel's own no-vig line. A value of 0 means there is no consensus. That happens on a one-sided market, such as an anytime touchdown that lists only "Yes", because there is no margin to take out.

fairProbability is rounded to six decimal places, and fairAmericanOdds to a whole number. get_player_props gives each prop the same values. Best price across books lists the books.

The same outcome also carries expectedValue, FanDuel's price measured against this fair chance. Expected value explains it.

RelatedCopy Anchor Link

• Vig and no-vig prices, the guide on the Unitley site.
• The no-vig fair odds calculator, to try a market in the browser.