plainodds

Prediction Market Odds Converter

Turn a Kalshi or Polymarket contract price into implied probability and American, decimal, and fractional odds. The price in cents is the probability.

Convert a contract price

A whole-dollar contract settles at $1. Enter the YES (or NO) price, 1–99¢. The other side = 100 minus this.

Prediction market pricing, plain

Why the price in cents IS the probability

On a prediction market like Kalshi or Polymarket, a contract settles at $1 if the event happens and $0 if it doesn't. So a contract trading at 65¢ means buyers and sellers collectively price the event at a 65% chance — pay 65¢ for a $1 payout, and the math only makes sense if the event happens about 65% of the time.

That's the clean part: unlike a sportsbook moneyline, where the implied probability is inflated by the vig, the prediction market price is the market's probability estimate directly (give or take the bid-ask spread and a small trading fee).

The conversion formulas

For a price of p cents:

  • Implied probability = p%
  • Decimal odds = 100 / p (e.g. 65¢ → 1.54)
  • American odds: if p > 50, −(p / (100 − p)) × 100; if p < 50, ((100 − p) / p) × 100

A 65¢ contract is a favorite (−186); a 35¢ contract is an underdog (+186). 50¢ is a true coin flip (+100 / even money).

YES vs NO — two sides of the same market

Every prediction market has a YES side and a NO side, and their prices sum to (about) 100¢. If YES is 65¢, NO is 35¢. Buying NO at 35¢ is the same bet as betting against the 65¢ YES — you collect $1 if the event does not happen. The small gap above 100¢ (the bid-ask spread) plus the trading fee is the market's cost, analogous to a sportsbook's hold but usually far smaller.