Polymarket odds are prices: a Yes share at $0.41 pays $1 if the event happens, so the market puts the chance at about 41%. On Nimb, that price is shown as a chance in % and moves are shown in points, never in cents or percent changes.
What does a price of 41% mean?
A share pays $1 if its outcome happens and $0 if it does not. If traders pay $0.41 for it, the market as a whole puts the chance at about 41%. Implied probability is the chance of an outcome that a share price implies: a share paying $1 that trades at $0.41 implies about 41%. It is also the chance at which buying the share would break even, before fees.
It is the crowd's estimate, not a forecast by Nimb or by Polymarket. Prices are set by traders on an order book, as explained in what are prediction markets.
How do I convert a Polymarket price to decimal or American odds?
Three formulas cover everything, with the price p written between 0 and 1:
- Chance = p × 100%. A price of 0.41 is 41%.
- Decimal odds = 1 / p. At 0.41, 1 / 0.41 = 2.44: every $1 you spend returns $2.44 if you are right.
- Profit per share = 1 − p. At 0.41, each share earns $0.59 if right and loses $0.41 if wrong.
American odds follow from the same price: below 0.50 they are +100 × (1 − p) / p; above 0.50 they are −100 × p / (1 − p).
| Price | Chance | Decimal odds | American odds | Payout per $1 spent | Profit per $1 spent |
|---|---|---|---|---|---|
| 0.20 | 20% | 5.00 | +400 | $5.00 | $4.00 |
| 0.41 | 41% | 2.44 | +144 | $2.44 | $1.44 |
| 0.50 | 50% | 2.00 | +100 | $2.00 | $1.00 |
| 0.75 | 75% | 1.33 | −300 | $1.33 | $0.33 |
| 0.90 | 90% | 1.11 | −900 | $1.11 | $0.11 |
All figures are before fees. Polymarket charges a taker fee on many markets, and Nimb adds a small builder fee, included in the price you see. On Nimb the amount you type is all-in, so a $100 Yes order at 41% buys slightly fewer than the 244 shares the table implies, and the ticket shows the break-even chance with fees. Details are on fees and all-in pricing.
Why don't Yes and No add up to exactly 100%?
Because there are two prices for each share, not one. The bid is the best price someone will pay; the ask is the best price someone will sell at. The gap is the spread.
On Polymarket, Yes and No trade on one book: buying No at $0.59 is the mirror of selling Yes at $0.41. So if Yes is bid at 40% and offered at 42%, No is bid at 58% and offered at 60%. Buying both at their asks costs 42% + 60% = 102%; selling both at their bids gets 40% + 58% = 98%. The mids, 41% and 59%, add to exactly 100%.
| Bid | Ask | Mid | |
|---|---|---|---|
| Yes | 40% | 42% | 41% |
| No | 58% | 60% | 59% |
| Sum | 98% | 102% | 100% |
A 2-point spread costs you about 1 point on the way in if you buy at the ask. In a thin market the spread can be 5 or 10 points, and the displayed chance is much less precise. See spread and order book depth.
In events with several outcomes ("Who will win…?"), the prices of all the Yes shares should add to about 100%, and they drift above or below by the spreads of every outcome.
Which price does Nimb show: last trade, mid or ask?
Nimb shows the mid price, halfway between the best bid and the best ask, as streamed from Polymarket's CLOB WebSocket. When the spread is wider than 10 points, the mid says little, so Nimb falls back to the last trade or the price Polymarket publishes for the market. A new trade also updates the price at once.
The price you pay is different: a buy fills at the ask and up the book, plus fees. The order ticket uses the live book for that, so its "If right" line can differ from the chance on the map by the half-spread and fees. Polymarket's own site follows a similar convention of showing the midpoint unless the spread is wide.
What is a point move?
A point is one percentage point of chance. Nimb always reports moves in points, because a percent change of a probability misleads.
- 41% → 45% is +4 points. It is not "+10%", even though 45 is about 10% more than 41.
- 2% → 4% is +2 points, a small change in chance, though the price doubled.
- 90% → 95% is +5 points, but the chance of No halved, from 10% to 5%.
Points let you compare moves across markets: +4 points means the same revision whether the market started at 20% or 70%.
Is the price the chance or the crowd's opinion?
It is the crowd's opinion of the chance, expressed in money, and it carries a few distortions:
- Risk preferences. Traders who like long shots push cheap prices up; those who need certainty pay up for favourites. Economists have shown that prices need not equal the average belief of traders, though under common conditions they come close (Manski, Economics Letters, 2006; Wolfers and Zitzewitz, NBER working paper 12200, 2006).
- Fees and the time value of money. Money tied up until resolution earns nothing. A share at 97% that resolves in a year may be fairly priced even if the event is near-certain.
- Thin books. A few trades can set the price.
- Rules. The price reflects the question as written, including how it will be resolved.
What can a price not tell you?
A price is a number, not an explanation. It does not say why traders moved, who they are, or whether they are right. Read it with the spread, the money traded and the holders (see how to read a market), and check how accurate markets tend to be at the price level you are looking at. Market reading starts with the price and does not end there.
From reading to execution
When you place an order, the order ticket turns the price into plain numbers: "You buy 237 Yes shares at 41% each. If it happens, you get $237.12. Otherwise you lose $100.00. Break-even 42.2% with fees." (An illustrative $100 order in a fee-charging market.) Prediction markets are risky and you can lose your whole stake.
Last reviewed 2026-11-07 · Data from Polymarket · Not financial advice · Nimb is not affiliated with Polymarket.