How do you convert American odds to decimal?

For positive American odds, decimal = 1 + odds/100. For negative odds, decimal = 1 + 100/|odds|. So +150 becomes 2.50 and -150 becomes 1.67.

What is implied probability?

Implied probability is the win chance baked into a price. For +150 it is 100/(150+100) = 40%. Decimal odds convert with 1/decimal. It is the number that actually matters when comparing a bet to your own estimate.

Is a Polymarket price the same as probability?

Yes. A Polymarket share priced at 40 cents implies a 40% chance the outcome happens. Cents map directly to implied probability, which is why prediction-market prices are so easy to read.

Odds Converter — American, Decimal & Implied Probability

Type any price in American odds, decimal odds, or Polymarket cents and instantly see the implied probability plus every other format. The win chance behind the number, in one place.

How the odds converter works

American odds, decimal odds, and Polymarket cents are three different costumes for the same underlying number: the implied probability of an outcome. This tool converts whatever you type into that probability first, then re-expresses it in every format. Change the input, and all four results update live.

The core formulas. Implied probability from American odds: for a plus price, 100 ÷ (odds + 100); for a minus price, |odds| ÷ (|odds| + 100). From decimal: 1 ÷ decimal. From cents: cents ÷ 100. To go back out: decimal = 1 ÷ probability, and American = +(decimal−1)×100 when decimal ≥ 2, else −100 ÷ (decimal−1).

Worked example

Take +150. Implied probability = 100 ÷ (150 + 100) = 40%. Decimal = 1 ÷ 0.40 = 2.50. In Polymarket terms that outcome is trading at 40¢. All three describe the exact same 40% bet — the only thing that changes is the notation your book or market happens to use.

Why implied probability is the number that matters

You can't compare a bet to your own read of the game while you're staring at -115. Convert it to a probability and the question becomes simple: do I think this is more likely than 53.5%? If yes, the price is offering value; if no, it isn't. Every edge you'll ever find is the gap between the implied probability of a price and your honest estimate of the true chance.

Polymarket note. On a prediction market, the price is the probability — a share at 40¢ means the market thinks there's a 40% chance, no conversion needed. That's why Polymarket prices read so cleanly: cents map one-to-one to implied percentage.

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Odds Converter

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How the odds converter works

Worked example

Why implied probability is the number that matters