Polymarket does not post odds the way a sportsbook does. It posts prices, and those prices are already probabilities. A share trading at 62¢ implies roughly a 62% chance the outcome happens. There is no line to decode and no plus-or-minus number to convert — the market is quoting the probability directly.
That simplicity hides a few things worth understanding: what you actually win at a given price, how to translate a Polymarket price into the American or decimal odds you may be used to, and why the price on the screen is not the price you get.
This is a companion to Polymarket Trading Basics, which covers the wider workflow. If you are brand new, What Is Polymarket? is the better starting point.
What do Polymarket odds actually mean?
Each market sells shares in an outcome. A share pays $1.00 if the outcome happens and $0 if it does not. Because the payout is fixed at a dollar, the price of the share is the market’s estimate of how likely that dollar is to arrive.
Buy a Yes share at 62¢ and you are making a specific trade: you risk 62¢ to win 38¢. That is only a good bet if you think the true probability is meaningfully above 62%.
The conversion is direct, so the mental arithmetic is easy:
- Price in cents = implied probability in percent. 7¢ is 7%. 45¢ is 45%. 93¢ is 93%.
- The counterpart costs the remainder. If Yes is 62¢, No should be close to 38¢.
One caveat before you lean on this too hard. A price is only a good probability estimate when the market is liquid enough for that reading to mean something. A thinly traded market with a wide spread and a handful of participants is quoting one opinion, not a crowd forecast.
What you win: payout and return at each price
The share always redeems at $1.00, so your profit is simply the gap between what you paid and that dollar.
| Buy price | Cost per share | Profit if it wins | Return | Break-even probability |
|---|---|---|---|---|
| $0.05 | 5¢ | 95¢ | 1,900% | 5% |
| $0.10 | 10¢ | 90¢ | 900% | 10% |
| $0.25 | 25¢ | 75¢ | 300% | 25% |
| $0.40 | 40¢ | 60¢ | 150% | 40% |
| $0.50 | 50¢ | 50¢ | 100% | 50% |
| $0.62 | 62¢ | 38¢ | 61% | 62% |
| $0.75 | 75¢ | 25¢ | 33% | 75% |
| $0.90 | 90¢ | 10¢ | 11% | 90% |
| $0.95 | 95¢ | 5¢ | 5% | 95% |
The formulas behind the table:
- Profit per share = $1.00 − price
- Return = (1 − price) ÷ price
- Break-even probability = the price itself
That last line is the one to remember. The price is your break-even. Buying at 90¢ only makes money if the outcome happens more than 90% of the time. The 11% return is not a small reward for a safe bet — it is the correct reward for a bet that loses your entire stake one time in ten. Cheap-looking shares work the same way in reverse: a 5¢ share returning 1,900% is not a lottery ticket priced wrong, it is a bet the market expects to lose 19 times out of 20.
How to convert Polymarket prices to American odds
If you came from sportsbooks, this is the translation you want. Let p be the price in decimal form (62¢ = 0.62).
- Underdogs (price of 50¢ or below): American odds = +(100 ÷ p) − 100
- Favorites (price above 50¢): American odds = −(100 × p) ÷ (1 − p)
An even-money 50¢ share sits on the boundary and is written either way, as +100 or −100.
| Polymarket price | Implied probability | American odds | Decimal odds |
|---|---|---|---|
| $0.10 | 10% | +900 | 10.00 |
| $0.20 | 20% | +400 | 5.00 |
| $0.25 | 25% | +300 | 4.00 |
| $0.33 | 33% | +203 | 3.03 |
| $0.40 | 40% | +150 | 2.50 |
| $0.50 | 50% | +100 | 2.00 |
| $0.60 | 60% | −150 | 1.67 |
| $0.62 | 62% | −163 | 1.61 |
| $0.70 | 70% | −233 | 1.43 |
| $0.75 | 75% | −300 | 1.33 |
| $0.80 | 80% | −400 | 1.25 |
| $0.90 | 90% | −900 | 1.11 |
Going the other direction, from American odds back to a price: for a positive line, price = 100 ÷ (odds + 100); for a negative line, price = odds ÷ (odds + 100), using the absolute value.
Decimal and fractional odds
Decimal odds = 1 ÷ price. A 40¢ share is 2.50 in decimal, meaning $1 staked returns $2.50 in total including your stake. This is the cleanest conversion of the three because decimal odds are just the reciprocal of probability.
Fractional odds = (1 − price) ÷ price, expressed as a ratio. A 25¢ share is 3/1. A 50¢ share is 1/1, or evens. A 75¢ share is 1/3.
Notice that fractional odds and the “return” column in the payout table above are the same number in different clothing. 3/1 and 300% describe an identical bet.
Why Polymarket odds look better than sportsbook odds
Here is the structural difference that matters most, and it is not a small one.
A sportsbook typically prices both sides of a coin flip at −110. That implies 52.38% for each side, which sums to 104.76%. That extra 4.76% is the overround, or vig — the house’s margin, baked into the line before anything happens.
On Polymarket, Yes and No are complementary claims on the same dollar, so their prices sum to approximately $1.00, or 100%. There is no built-in overround, because the platform is not taking the other side of your bet. It is matching you against another trader.
This does not make trading free. Your costs move somewhere else:
- The spread between the best bid and the best ask.
- Slippage when your order is larger than the depth sitting at the best price.
- Any platform fees applicable to the market you are trading, which you should confirm at trade time rather than assume.
The honest comparison is that Polymarket replaces a fixed, guaranteed house margin with a variable cost that depends on how liquid your specific market is. In a deep market that is a real advantage. In a thin one, the effective cost can be worse than the vig you were avoiding. Prediction Markets vs Sportsbooks goes deeper on how the two models differ.
When Yes and No don’t add up to $1
In a well-functioning market, Yes + No lands very close to $1.00. When it does not, it usually means one of three things.
If the sum is meaningfully below $1.00 across the best available asks, that is theoretically a locked profit — buy both sides, collect a dollar whichever way it goes. In practice these gaps are small, short-lived, and often smaller than the cost of executing both legs.
If the sum sits above $1.00, you are looking at the spread rather than a mispricing. Comparing the best ask on Yes against the best ask on No double-counts the spread; compare mid prices instead.
And in multi-outcome markets, the arithmetic changes: probabilities across all outcomes should sum to roughly 100%, not any individual pair.
The price you see is not the price you get
This is where the neat arithmetic above meets reality. The number displayed on a market is usually the mid — halfway between the best bid and the best ask. You cannot trade at the mid. You buy at the ask and sell at the bid.
In a market quoted 61¢ bid / 63¢ ask, the mid reads 62¢, but buying costs you 63¢. That single cent has moved your break-even probability from 62% to 63% and shaved your return from 61% to 59%. On one trade it is noise. Across a hundred trades it is the difference between a profitable process and a losing one.
Size makes it worse. If only a few hundred dollars of depth sits at 63¢, a larger order walks up the book and fills at a worse average price than the quote suggested. Before entering, it is worth glancing at three numbers rather than one: the mid, the price you would actually pay, and how much size is available near it. Polymarket Trading Basics covers execution and liquidity in more detail.
Odds are not certainty: reading a 90% market correctly
A well-calibrated 90% market should be wrong one time in ten. That is not a failure of the market — it is what 90% means. If every 90% market resolved Yes, the price would be 100¢.
Two errors follow from forgetting this. The first is treating a high price as a sure thing and sizing accordingly, then being genuinely shocked by an outcome the price openly warned about. The second is looking at a market that resolved against the favorite and concluding the market was “wrong.” A single outcome cannot tell you whether a probability was accurate. Only a long run of them can.
The useful habit is to judge your own forecasts the same way: over many trades, do the things you called 70% happen roughly 70% of the time? That question is answerable and it is the only real measure of whether you have an edge.
Watching odds move
Prices are most informative when they change, because a repricing is the market telling you that someone’s information or conviction shifted. But a price is only useful to you if you notice it while it still matters.
Rather than refreshing tabs, you can set thresholds and get notified when a market crosses a price or moves by a percentage you define. Polymarket Alerts does this for price moves, whale trades, and specific traders’ activity, and the Features page shows how the alert types fit together. The point is not to react to every wiggle — most movement is noise — but to be present for the moves that actually change your thesis.
Frequently asked questions
How do Polymarket odds work? Prices are probabilities. A share costs between $0 and $1 and pays $1 if the outcome happens, so a 62¢ price implies about a 62% chance.
How much do I win on Polymarket? $1.00 per winning share, minus what you paid. Buy at 40¢ and you profit 60¢ per share, a 150% return.
How do I convert Polymarket prices to American odds? For prices of 50¢ or below, use +(100 ÷ price) − 100. For prices above 50¢, use −(100 × price) ÷ (1 − price). A 40¢ share is +150; a 75¢ share is −300.
Why don’t Yes and No add up to exactly $1? Usually because you are comparing two asks, which double-counts the spread. Compare mid prices. Genuine gaps do occur but are small and short-lived.
Are Polymarket odds better than a sportsbook’s? There is no built-in vig, since Yes and No sum to about $1 rather than a sportsbook’s typical 104-ish%. Your cost is the spread and slippage instead, which is cheaper in liquid markets and can be worse in thin ones.
Does a 90% price mean it’s guaranteed? No. A calibrated 90% market should resolve No about one time in ten, and buying at 90¢ loses your full stake when it does.
Related reading
- Polymarket Trading Basics — execution, liquidity, sizing, and building a repeatable process.
- Prediction Markets vs Sportsbooks — how the two pricing models differ.
- Prediction Market Strategy: Risk and Reward — turning probabilities into position sizes.
- How Polymarket Resolution Works — how a share becomes a dollar.
Bottom line
Polymarket odds are the easiest odds in trading to read, because the price is the probability and the price is your break-even. The arithmetic that matters fits in two lines: you profit $1 minus what you paid, and you need the outcome to happen more often than the price implies. Everything difficult sits around the edges — the spread you pay to get in, the depth that determines your real fill, and the discipline to remember that a 90% market is supposed to be wrong sometimes.
This article is educational and not financial advice. Fees and market mechanics change — confirm current details on Polymarket before trading.