Prediction Market Odds Converter

A Yes contract priced at 65 cents costs $0.65 and pays $1.00 if the event occurs. The implied probability is the price in cents divided by 100. At 65 cents: 65% implied. At 30 cents: 30% implied. No conversion tables needed.

The complementary No contract is priced at 100 minus the Yes price. If Yes is 65 cents, No is 35 cents. In theory, the two implied probabilities sum to 100% - prediction markets do not embed a hold the same way sportsbooks do, though fees create a similar drag.

Kalshi charges taker fees that are highest near the midpoint (50 cents) and lower toward the extremes. Polymarket historically has not charged explicit fees on most markets. Factor these costs in when comparing net returns to a sportsbook bet.

If the implied probability is 65% (0.65), the event is the favorite. American = -(probability / (1 - probability)) x 100 = -(0.65 / 0.35) x 100 = -186.

If the implied probability is 35% (the No side), the event is the underdog. American = ((1 - probability) / probability) x 100 = (0.65 / 0.35) x 100 = +186. The No contract at 35 cents equals +186 American.

The Reverse Check field shows what cents price you recover after converting to American and back. A small difference (1-2 cents) is normal rounding. Larger differences indicate an input problem.

Enter the midpoint price from the prediction market, not the bid-ask spread. If the market shows 64-66 cents, enter 65. Use the midpoint for a clean comparison against sportsbook mid-prices.

Reverse Check is most useful when you are converting American odds back to cents to verify consistency. If the round trip drifts by more than 2 cents, check your original input.

A candidate in a political market trades at 65 cents. That implies 65% probability and converts to -186 American. You check three sportsbooks and find the same candidate at +175 American.

The sportsbook +175 implies 36.4% win probability. The prediction market No contract at 35 cents implies 35%. The 11-cent gap between +175 at the sportsbook and the implied -186 equivalent is the cross-market difference.

After accounting for Kalshi taker fees near the 35-65 midpoint (roughly 2%), the sportsbook No-equivalent bet at +175 still looks better on a net return basis. That is the kind of cross-market comparison this calculator makes easy.

Settlement timing is a risk unique to prediction markets. A sports bet settles at final score. A prediction market may settle on official certification days later. During that window you carry open risk even if your edge is correctly identified.

Liquidity at the extremes (below 10 cents or above 90 cents) is often thin. Large orders move the price significantly and effective execution may differ substantially from the quoted midpoint.

Not all sportsbooks offer odds on political or macro events. The cross-market comparison is most useful for sports and financial events that both platforms cover with meaningful liquidity.