Polymarket Odds API

Decimal odds = 1 / price; American odds = (price / (1 - price)) * 100 for a favorite-positive or the negative convention of the closing line. The conversion is exact arithmetic, and the honest odds value is the executable side, not the mid.

The venue's own free surface (live odds) is the same data in probability form; an "odds API" is a relabeling of the price contract, which is why this page maps every endpoint back to the price and book ground truth.

Odds conversion changes the unit, not the meaning: a 0.99 bunching executable price is +9900-style odds that no one trades at — the honest odds feed pairs a price with its depth so the number is never mistaken for a level at which you could fill.

Polymarket's native unit is probability, and an odds feed is a relabeling of the same price contract: decimal odds are 1 divided by price, American odds are the closing-line convention of the executable side. The conversion is exact arithmetic; the honest odds value is the executable price, not the mid, because the mid can be imaginary on one-sided frames.

The endpoints on this page therefore map every odds surface back to the price and book ground truth, so a study can always recover the probability beneath the label.

• Market price API
• Live odds
• Odds explained