Polymarket Probability & Payout Calculator
Enter a Polymarket price and stake to see implied probability, decimal odds, shares, gross payout, and profit before fees — with the arithmetic visible.
Affiliate disclosure: Business Dog may earn money if you open or use Polymarket through a qualifying link here. That does not change the math, the verdict, or the price you see. Yes, this link can make us money.
At this price, the position buys about 100.000 shares. A winning share redeems for $1; a losing share redeems for $0. Displayed probability is not a promise.
A Polymarket share priced at 65¢ implies roughly 65%. Spending $65 at that exact price buys 100 shares, which pay $100 gross if the selected outcome wins: $35 profit before fees. If it loses, the position is worth $0.
What does the calculator assume?
It assumes your entire entered amount fills at the entered price. It does not fetch an order book, claim a live quote, include Predictions taker fees, or estimate slippage. Those omissions are visible because hiding assumptions is how calculators become decorative lies.
The formulas are:
probability = price in cents ÷ 100
decimal odds = 1 ÷ probability
shares = stake ÷ probability
gross payout if correct = shares × $1
profit before fees = gross payout − stake
For a fuller explanation of outcome shares, order books, and resolution, start with how Polymarket works. For current category-dependent costs, use the Polymarket fee calculator.
Why can payout look huge on a low-probability share?
At 5¢, one dollar buys 20 shares. If the outcome wins, those shares pay $20 gross. That does not mean the trade discovered a free 20× machine in an abandoned office park. The market price is saying the outcome is unlikely.
The payout expands because the estimated chance contracts.
| Share price | Implied probability | Decimal odds | $10 gross payout if correct |
|---|---|---|---|
| 90¢ | 90% | 1.111× | $11.11 |
| 65¢ | 65% | 1.538× | $15.38 |
| 25¢ | 25% | 4.000× | $40.00 |
| 5¢ | 5% | 20.000× | $200.00 |
Why might the screen and the fill disagree?
The displayed Polymarket price can be the midpoint between the best bid and ask. If YES shows 65¢ but the best ask is 68¢, a buyer demanding immediate execution may pay 68¢. A larger order may consume offers above 68¢ too.
Use the fill price for post-trade arithmetic. Use the order book for pre-trade planning. Use the midpoint only for what it is: a summary of two sides that have not agreed yet.
Can probability be added across several picks?
Not the way people hope. Three separate 90% legs do not create 270% certainty. Under independence they create:
0.90 × 0.90 × 0.90 = 0.729 = 72.9%
That is why a separate Polymarket Combo calculator multiplies legs, reports the chance at least one fails, and warns about correlation.
Does 65¢ mean Polymarket says the event has exactly a 65% chance?
It means the current market price implies roughly 65%. Market prices move and can be miscalibrated. The number is evidence about collective trading belief, not certification from the Department of Future Events.
Does gross payout include my stake?
Yes. If you spend $65 and receive $100 when correct, the $100 gross payout includes the $65 originally spent. Profit before fees is $35.
Why are fees not included?
Predictions fees depend on market category, maker/taker status, price, and shares. Keeping the payout tool independent of a category guess prevents it from displaying a precise-looking wrong fee. Use the linked fee calculator next.
The calculator knows division. It does not know the future. CowDog has been informed of the distinction.
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This article is educational and satirical content from Business Dog. It is not financial, legal, or tax advice. It's just business.