How to Read and Compare Prediction Market Odds

Reading prediction-market odds is easy once you internalize one rule: the price is the probability. The real money, though, is in noticing that the same event is priced differently across platforms — and buying where it's cheapest.

Price is a percentage

Contracts settle at $1 (event happens) or $0 (it doesn't), so a price can only sit between them — and it maps straight onto a probability:

• 25¢ = a 25% implied chance.
• 50¢ = a genuine 50/50.
• 80¢ = an 80% implied chance.

Some platforms quote in cents ($0.80), others show a percentage (80%) or decimal odds — but they all describe the same thing. This is called implied probability. New to the idea? Start with what prediction markets are.

Yes and No add up to $1

For any binary market, the Yes and No prices sum to $1 (100%). If "Yes" is 70¢, "No" is 30¢. That relationship is a quick sanity check and the basis for spotting arbitrage: if you can ever buy Yes and No for less than $1 combined (across the same or different platforms), you lock in a guaranteed profit at settlement.

Converting between formats

To move between how different venues display odds:

• Cents → probability: a 65¢ price is a 65% chance. Just read the cents as a percent.
• Probability → cents: a 35% chance is a 35¢ price.
• Probability → decimal odds: divide 1 by the probability. A 40% chance (0.40) is decimal odds of 1 ÷ 0.40 = 2.5.
• Decimal odds → probability: divide 1 by the odds. Decimal 4.0 = 1 ÷ 4.0 = 25%.

Comparing platforms: line shopping

Here's the part most beginners miss. The same event — say "Will candidate X win?" — can trade at 61¢ on one platform and 58¢ on another at the same moment. Buying the 58¢ side means you pay less for the identical payout. Over many trades, consistently taking the better price is one of the most reliable edges there is. Sports bettors call it line shopping; the logic is identical here.

This is exactly what a prediction market aggregator is for. MarketsPrediction lines up the same event across Polymarket, Kalshi, and Predicta so you can see, at a glance, who has the best price — no tab-juggling required. Browse them on the homepage.

Mind the hidden costs

A "better" headline price isn't always better once costs are included. Two things quietly move your real price:

• The bid-ask spread — you buy at the higher ask and sell at the lower bid, so a wide spread costs you on both ends.
• Trading fees — a small per-trade or settlement fee can erase a one-cent price advantage.

On thin markets you may also face slippage, where a large market order walks up the order book and fills at a worse average price than the quote. Favor markets with real liquidity.

Watch for longshot bias

Markets aren't perfectly efficient. A well-documented quirk is longshot bias: very unlikely outcomes (say, 3¢ contracts) often trade a touch too high because people overpay for lottery-style upside, while heavy favorites can be slightly underpriced. Knowing where the crowd systematically errs is itself an edge.