Polymarket Odds Converter

How to use this converter

Enter the YES price in cents. A share pays $1.00 if it resolves YES, so a 64¢ share implies a 64% chance and decimal odds of 1 / 0.64 = 1.5625, or -178 in American terms. The NO side is shown at 1 − price. Enter the actual NO price as well and the converter reports the spread: how far the two sides add up beyond 100¢, which plays the same role as a bookmaker's vig.

How Polymarket prices work

Every binary market has two shares, YES and NO. Each pays $1.00 if it resolves in its favour and nothing otherwise. The price of a share, in cents, is therefore the market's probability: buy 100 YES shares at 64¢ for $64, and if YES resolves you receive $100, a profit of $36. On a liquid market YES and NO add up to about 100¢, because holding one of each returns exactly $1.00.

That makes a Polymarket price simpler than any odds format, but it hides the same things a bookmaker's price hides: a margin (the spread) and the difference between a quoted price and a fair probability.

Converting a price to odds

Because the price is already a probability, converting is a matter of dividing:

• Decimal odds are 1 / price. 64¢ is 1.5625; 25¢ is 4.00.
• American odds follow from the decimal: 1.5625 is -178 (risk 178 to win 100), 4.00 is +300.
• Fractional odds are the decimal minus one: 64¢ is 9/16, 25¢ is 3/1.

The reverse also works. A sportsbook price becomes a Polymarket price by taking its implied probability in cents: -150 is 60%, so it would trade near 60¢; +200 is 33.3%, near 33¢. The odds converter accepts cents directly if you want every format for a single price.

What the spread tells you

The spread is YES + NO − 100¢. If YES is 64¢ and the best NO price is 38¢, the spread is 2¢: buying both sides costs $1.02 for a guaranteed $1.00 back, so the 2¢ is the market's margin, the same role a bookmaker's overround plays. A 2¢ spread near 50¢ is tight, roughly a two-way sportsbook market at -102 each side. The same 2¢ on a 5¢ / 97¢ market is proportionally large: the YES side is 20.0 decimal, and one cent either way moves that to 16.7 or 25.0.

The headline price on a market is usually the last trade or the midpoint between bid and ask. The price you pay is the best ask, and on a thin market that can be several cents higher. Use the ask for any comparison where you intend to buy.

How fees change the effective price

Where a trading fee applies it comes off the profit, so it works like exchange commission on net winnings: effective decimal = 1 + (decimal − 1) × (1 − fee). With an illustrative 2% fee, a 64¢ share's 1.5625 becomes 1.551, and the effective probability you are paying for rises from 64.0% to 64.5%. Fee schedules change and differ by market category, so this site does not hardcode a rate; check the fee on the market you are trading in your own account and enter it where the calculators ask for one. Gas and withdrawal costs sit outside the price and are ignored here.

Comparing a Polymarket price with a bookmaker line

Line the two up as decimal odds: the Polymarket side after fees, the bookmaker side as displayed, because its margin is already in the price. A 64¢ YES share is 1.5625 before fees. A bookmaker offering -170 on the same outcome is 1.588, so the bookmaker is the better price on that side. On the other side, NO at 38¢ is 2.63; if the bookmaker offers +150 (2.50) on the opposite outcome, the market is better there. Compare each side separately; the venues often disagree in opposite directions.

When they disagree by more than the spread and fees, the two form an arbitrage: buy YES on the market and back the opposite outcome at the bookmaker. YES at 64¢ (1.5625) against a bookmaker's 2.90 (+190) on the other side sums to 98.48%, and 100 split 64.99 / 35.01 returns 101.54 either way, a 1.54% profit before fees. The arbitrage calculator sizes it with the Polymarket preset on one leg.

Frequently asked questions

Is a 64¢ share the same as -178?

Yes, before fees. Both mean you risk 64 to win 36. A sportsbook offering better than -178 on the same event is the better price.

Why do YES and NO add up to more than 100¢?

That is the spread between the best bid and ask. Buying both sides at those prices costs more than the $1.00 they pay back, which is why the spread is the market's margin.

Is the price the probability?

It is the market's probability including the spread and any fee, and on a thin market the last trade can be stale. For a fair estimate use the midpoint of a liquid market, or divide each side by the sum of the two: 64 / (64 + 38) = 62.7% for YES.

Can I arbitrage Polymarket against a sportsbook?

If the sportsbook's odds on the opposite outcome are long enough, yes. Use the arbitrage calculator with the Polymarket preset on one leg, and for a group of markets that together cover every outcome, the Polymarket arbitrage calculator.

Does this work for Kalshi prices?

Yes. Kalshi contracts are priced in cents the same way; the Kalshi page has this converter pre-set alongside the fee tables. The Polymarket odds guide goes further into order books, resolution rules and slippage, and How Polymarket works covers the platform itself: who trades, how markets resolve and where it is legal.

Every cent value from 1¢ to 99¢ has its own page under Polymarket prices with payouts and neighbouring prices.