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▌ Calculator · implied odds · updated 2026-05-09

Probability in.
Fair odds out.
Instantly.

Every win estimate has a matching fair price. If you believe something has a 40% shot, the line that breaks even over time is +150 American. The market offering +130 is underpriced. The market offering +175 is giving you edge.

Implied odds are the bridge between your model and the sportsbook's board. Enter your probability estimate and the calculator returns the exact fair price in every format — American, decimal, fractional. Line-shop against it directly.

Convert probability See the formula

Calculator

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▌ Probability input

%

Common probabilities

Formula: decimal = 1 ÷ (probability ÷ 100)
At 52.38% → 1 ÷ 0.5238 = 1.909 (decimal) = -110 (American)

▌ Fair odds at this probability

American odds

-110

0% 50% 100%

Decimal

1.909

Fractional

10/11

Implied prob

52.38%

▌ Derivation · implied odds formula

The fair odds formula

Decimal odds equal total return per unit staked. If the true probability of winning is p, the fair decimal price that produces zero expected value over many bets is decimal = 1 / p (where p is expressed as a fraction, not a percentage). At p = 0.40: decimal = 1/0.40 = 2.50.

Converting 2.50 decimal to American: since 2.50 > 2.00 (underdog), American = (decimal − 1) × 100 = 1.50 × 100 = +150. For favorites below 2.00 — say p = 0.65, decimal = 1/0.65 = 1.538: American = −(1/(decimal−1)) × 100 = −(1/0.538) × 100 = −186.

Fractional odds represent net profit per unit staked. Fractional = decimal − 1. At 2.50 decimal: fractional = 1.50 = 3/2 = 3-to-2. The numerator and denominator are reduced to integers by finding the least common multiple over two decimal places. This calculator uses standard fraction reduction up to 64-denominator precision.

Edge detection with implied odds

Enter your model's probability. The calculator returns the fair line. Compare the fair line against the offered line on the sportsbook. If the offered price is longer (better) than the fair line, you have positive expected value. The gap between offered and fair is the edge — expressed either in probability points or in EV per dollar wagered.

Strip bookmaker margin first. Use the no-vig calculator to convert a two-sided market into fair probabilities. Then enter those fair probabilities here to confirm the implied odds match what you derived manually.

The reverse operation — odds into probability — is covered by the implied probability calculator. Both tools share the same underlying formula; only the direction differs.

▌ Reference

Common probabilities to odds

Probability American Decimal Fractional
16.67% +500 6.000 5/1
25.00% +300 4.000 3/1
33.33% +200 3.000 2/1
40.00% +150 2.500 3/2
50.00% +100 2.000 Evens
52.38% −110 1.909 10/11
60.00% −150 1.667 2/3
66.67% −200 1.500 1/2
75.00% −300 1.333 1/3
80.00% −400 1.250 1/4

▌ FAQ

Common questions

What are implied odds in betting?
Implied odds translate a probability into the fair-value betting price. If you believe an outcome has a 40% chance of winning, the fair decimal odds are 1 / 0.40 = 2.50, which is +150 in American format. Any price shorter than 2.50 (e.g. 2.30) means you are paying above fair value; any price longer (e.g. 2.80) means the line offers an edge. Implied odds are the baseline you compare every offered line against.
How do I convert probability to American odds?
For favorites (probability > 50%): American = −(probability / (100 − probability)) × 100. At 60%: −(60 / 40) × 100 = −150. For underdogs (probability < 50%): American = ((100 − probability) / probability) × 100. At 40%: (60 / 40) × 100 = +150. At exactly 50%, fair odds are +100 (evens). The calculator handles all three cases automatically.
What is the difference between implied odds and implied probability?
These are inverses of the same concept. Implied probability starts from a price and tells you what win rate it encodes. Implied odds start from a win rate and tell you the fair price. The formula is symmetrical: probability = 1 / decimal, decimal = 1 / (probability / 100). Use the implied probability calculator when you have a line and want to extract the bookmaker's embedded expectation. Use this calculator when you have a model probability and want the matching fair line.
How do I use implied odds to find value bets?
Enter your estimated win probability. The calculator returns the fair odds. Now check the actual line offered. If the sportsbook offers better odds than the fair line, you have a value bet — the edge is positive. Example: your model says 45% for a team to win. Fair odds = 1 / 0.45 = 2.222, which is +122 American. The book posts +140. Since +140 > +122, the book is offering better than fair value. Kelly criterion fraction for this edge: f = (0.45 × 1.40 − 0.55) / 1.40 = 0.055 = 5.5% of bankroll.
How does implied odds link to Kelly criterion bet sizing?
Once you have the fair decimal odds from your probability, Kelly optimal stake is f = (p × b − (1 − p)) / b, where p is your estimated probability and b is decimal odds minus 1. For p = 0.45 and fair decimal = 2.222 (b = 1.222): f = (0.45 × 1.222 − 0.55) / 1.222 = 0. You break even — no bet. But if the actual line is 2.50 (b = 1.50): f = (0.45 × 1.50 − 0.55) / 1.50 = 0.083 = 8.3% of bankroll. The Kelly fraction grows with the gap between fair and offered odds.
What probability corresponds to -110 (standard US line)?
Working in reverse: -110 American converts to 1.909 decimal. The implied probability is 1 / 1.909 = 52.38%. To find fair odds for a 52.38% probability estimate: decimal = 1 / 0.5238 = 1.909 = -110 American. So if you estimate exactly 52.38%, the standard -110 line is fair. You need to believe the true probability exceeds 52.38% to have a positive-edge bet at -110.

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