Prediction market odds converter: probability to American, decimal and fractional odds

Key takeaways

• A prediction market price in cents is its implied probability: 65¢ = 65%.
• Under 50¢: American odds = +(100 − price) ÷ price × 100. Over 50¢: −price ÷ (100 − price) × 100.
• Decimal odds = 100 ÷ price. 40¢ = 2.50.
• Fees make your real odds a little worse: a 50¢ Kalshi taker trade works out to about −107.

How do you convert a prediction market price to American odds?

A contract pays $1 if it wins, so its price in cents is the implied probability, P. From there:

• Under 50¢ (an underdog): American odds = +(100 − P) ÷ P × 100. A 30¢ contract is 70 ÷ 30 × 100 = +233.
• Over 50¢ (a favorite): American odds = −P ÷ (100 − P) × 100. A 65¢ contract is 65 ÷ 35 × 100 = −186.
• 50¢: even money, +100.
• Decimal odds = 100 ÷ P. A 40¢ contract is 2.50.
• Fractional odds = (100 − P) / P, reduced. A 25¢ contract is 3/1.

How do you convert American odds to a price?

• Positive odds (+X): price = 100 ÷ (X + 100). +150 is 100 ÷ 250 = 40¢.
• Negative odds (−X): price = X ÷ (X + 100). −150 is 150 ÷ 250 = 60¢.

A sportsbook's two sides add up to more than 100% because the book's margin is built in: −110 on both sides is 52.4% + 52.4%. On an exchange the two sides sit close to 100%, a cent or two apart. See prediction markets vs. sportsbooks.

How do fees change the odds?

Exchange fees are added to what you pay, so they lower the odds you really get. Both Kalshi and Novig charge rate × price × (1 − price) per contract where a fee applies:

• A 50¢ Kalshi taker trade at the reported 0.07 rate costs 51.75¢ all-in: about −107 instead of +100.
• A 25¢ Kalshi taker trade costs about 26.3¢: about +280 instead of +300.
• A Novig pregame straight trade has no fee, so the price is the odds.

Choose a fee in the converter above to see the effect at any price, or read fees compared.

Prediction market odds table: 1¢ to 99¢

Frequently asked questions

Sources

1. Kalshi Help Center: How are prices determined?
2. Novig Support: Fees on Novig
3. Allium: Kalshi fees, why the cost peaks near 50 cents

Facts that change, such as fees, rules and where each exchange operates, were checked on the date above. Check the exchange's own pages before you trade.

Sports Index Markets Every college football price in one place Novig and Kalshi side by side, with price history, strategies with graded records and the twice-weekly Betting Roundup. Open Markets →

Keep reading

Sports Index publishes research and paper picks; it is not a sportsbook or an exchange and takes no bets. Trading on prediction markets risks real money. You must meet the exchange's age requirement and be in an eligible state. If gambling is a problem for you or someone you know, call or text 1-800-GAMBLER.