BLAKbets

Odds-to-probability calculator

Enter odds in any format to see implied probability. Or enter your estimate to calculate fair odds.

Odds → probability

Odds format
Implied probability
40,00%
1 / decimal odds
Decimal odds
2,500

Probability → odds

Fair odds
2,50
decimal, no margin
American
+150
Fractional
3/2

Pure maths. No sign-in needed. Amounts are in USD, just like the platform.

Let the scanner find your next opportunity

The calculator does the maths. BLAKbets finds the opportunities, with over 143 arbs detected daily, calculated stakes, freshness indicators and direct sportsbook links.

View plans

No trial period. See plans and prices on the homepage. Adults aged 18+ only.

Formula

How odds become probability

  1. 01

    Convert to decimal odds

    American +150 = 1 + 150/100 = 2.50; −200 = 1 + 100/200 = 1.50. Fractional 3/2 = 1 + 3/2 = 2.50.
  2. 02

    Divide 1 by the odds

    Probability = 1 / decimal odds. 2.50 gives 1 / 2.50 = 40%.
  3. 03

    Reverse it: divide 1 by probability

    Fair odds = 1 / probability. A 40% probability gives odds of 2.50; 25% gives 4.00.

Example

Example: American odds −150

Questions

Frequently asked questions

What is implied probability?

The probability implied by a price: 1 / decimal odds. Odds of 2.50 imply 40%. The price includes margin, so it isn't an unbiased probability estimate.

Why convert probability to odds?

If you estimate 40%, fair odds are 2.50. A higher price has positive expected value under your estimate; a lower one does not.

Why do implied probabilities total more than 100%?

Sportsbook prices include margin. Calculate it in the margin tool. Best prices across sportsbooks totalling less than 100% create an arb.

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