ASTRA QUANTHow prediction market odds work
In a prediction market the “odds” are not set by a bookmaker — they are the current price of a contract that pays $1 if an outcome happens. This guide explains how to turn that price into a probability, into decimal odds, and what the spread tells you.
Updated: 1 November 2026. Educational material, not financial advice. Astra Quant is independent and not the official Polymarket site.
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Price = implied probability
Every outcome contract settles at $1 if it wins and $0 if it loses. So a price of 42¢ means you pay 42 cents for a chance to receive 100 cents. The implied probability is simply the price divided by the payout: 0.42 / 1.00 = 42%. That is the core rule of prediction market odds: cents ≈ percent.
Converting to decimal and fractional odds
If you are used to sports betting odds, you can convert in a line:
- Decimal odds = 1 / price. At 42¢: 1 / 0.42 ≈ 2.38. A $10 stake returns about $23.80 if the outcome wins (before any fees).
- Fractional odds = (1 − price) / price. At 42¢: 0.58 / 0.42 ≈ 1.38/1, roughly 11/8.
- American odds: below 50¢ it is +100 × (1 − p) / p (42¢ → about +138); above 50¢ it is −100 × p / (1 − p) (70¢ → about −233).
You can do these conversions instantly in the prediction market probability calculator.
Why Yes + No is not exactly 100¢
In theory the Yes price and the No price add up to $1, because exactly one of them will pay out. In practice you see two prices for each side: the best price someone will buy at (bid) and the best price someone will sell at (ask). If Yes can be bought at 43¢ and No at 58¢, the total is 101¢. The extra cent is the spread — the cost of trading immediately instead of waiting for someone to meet your price.
The mid-point between bid and ask is the cleanest estimate of the probability. Busy markets usually have a spread of about a cent; quiet ones can have several cents, which makes the displayed probability less reliable.
What moves the odds
- New information — a poll, an injury report, an inflation number, a sharp crypto move.
- Order flow — a large buyer can push the price up, especially in thin markets.
- Time — as the deadline approaches, uncertainty shrinks and prices drift toward 0 or 100.
- Rules — clarifications about how a market resolves can change its price sharply.
Liquidity and volume: how much to trust a price
Liquidity is how much is available to trade near the current price; volume is how much has actually traded. A price backed by high liquidity and recent volume reflects many people’s money. A price in a market with almost no liquidity can be moved by one small order. That is why Astra Quant shows 24-hour volume and liquidity next to each market — check them before reading too much into a number.
Multi-outcome markets
Some events have many possible results — “Who will win the tournament?” or “Which party wins the House?”. These are usually built as a set of separate Yes/No markets, one per candidate. Each candidate’s Yes price is its implied probability, and across all candidates the prices should add up to roughly 100%. If they add up to noticeably more, the difference is spread and pricing friction rather than extra information.
Probability is not certainty
A well-calibrated market at 70% will be wrong about three times in ten. Reading odds correctly means asking whether you think the true chance is higher or lower than the price, not whether the event “will” happen. A step-by-step routine for this is in How to read a Yes/No market.
Where the prices come from on Astra Quant
Prices on Astra Quant are based on public Polymarket data and update automatically. Astra Quant is independent and not the official Polymarket site. For the basics of the format, start with What is a prediction market; for the detailed walk-through with formulas, see How a contract price becomes a probability (Russian). You can practise with 1000 ASCD demo tokens that come with a new account; they have no monetary value.
Frequently asked questions
How do you read prediction market odds?
Read the price in cents as a probability in percent. A Yes price of 42¢ means the market puts the chance of Yes at about 42%.
How do I convert a price to decimal odds?
Divide 1 by the price in dollars. 42¢ is 1 / 0.42 ≈ 2.38 in decimal odds.
Why do Yes and No add up to more than 100¢?
The difference is the spread between buy and sell prices. The mid-point between bid and ask is the best single estimate of probability.
Do higher odds mean the event will happen?
No. A price is an estimate. A 70% outcome still fails roughly three times out of ten.
New accounts receive 1000 ASCD demo tokens — virtual, with no monetary value.