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Free · runs in your browser · no signup · live ladders updated September 25, 2026
Polymarket often asks one question with several deadlines — “by October 31”, “by December 31”. Later deadlines include the earlier ones, so the Yes prices form a ladder, and the gaps between them are the market's chance for each period. This calculator reads the ladder: the chance for each period if nothing has happened before it, the constant chance per month that implies, and the price each deadline should drift to if nothing happens by a date you pick. It also flags a later deadline priced below an earlier one, which is a mispricing. Example: 20¢ by October 31 and 35¢ by December 31 leave (35 − 20) ÷ (100 − 20) = 18.8% for the time in between, if nothing has happened by October 31.
| Deadline | Days left | Yes price | This period, if nothing earlier | Per month | If nothing by Oct 31, 2026 |
|---|---|---|---|---|---|
| Oct 31, 2026 | 36 | 20.0¢ | 20.0% | 17.2% | — |
| Dec 31, 2026 | 97 | 35.0¢ | 18.8% | 9.8% | 18.8¢ |
| Mar 31, 2027 | 187 | 50.0¢ | 23.1% | 8.5% | 37.5¢ |
A month is 365.25 ÷ 12 days. Days are counted between the dates, so the result for a deadline a few days away moves a lot with each day.
Say that on September 25, 2026 a question trades at 20¢ by October 31, 35¢ by December 31 and 50¢ by March 31, 2027 — the calculator above starts with these numbers.
The chance per month falls from one period to the next: the market prices the most risk now and less later. Over all 187 days, 50¢ works out at 10.7% a month on average.
The most traded “by date” questions on Polymarket with at least three deadlines still ahead, read the same way on September 25, 2026. Prices are the ones on our odds pages (midpoints, or the last trade when the spread is wide), refreshed twice a day.
| Deadline | Days left | Yes price | This period, if nothing earlier | Per month |
|---|---|---|---|---|
| Sep 30, 2026 | 5 | 8.5¢ | 8.5% | 41.8% |
| Oct 15, 2026 | 20 | 18.5¢ | 10.9% | 20.9% |
| Oct 31, 2026 | 36 | 30.5¢ | 14.7% | 26.1% |
| Nov 30, 2026 | 66 | 47.0¢ | 23.7% | 24.0% |
| Dec 31, 2026 | 97 | 61.6¢ | 27.5% | 27.1% |
| Mar 31, 2027 | 187 | 77.5¢ | 41.4% | 16.5% |
| Deadline | Days left | Yes price | This period, if nothing earlier | Per month |
|---|---|---|---|---|
| Sep 30, 2026 | 5 | 0.15¢ | 0.15% | 0.91% |
| Dec 31, 2026 | 97 | 4.3¢ | 4.1% | 1.4% |
| Jun 30, 2027 | 278 | 11.5¢ | 7.6% | 1.3% |
| Deadline | Days left | Yes price | This period, if nothing earlier | Per month |
|---|---|---|---|---|
| Sep 30, 2026 | 5 | 0.70¢ | 0.70% | 4.2% |
| Oct 31, 2026 | 36 | 8.5¢ | 7.9% | 7.7% |
| Dec 31, 2026 | 97 | 19.0¢ | 11.5% | 5.9% |
Each deadline's Yes price is the market's chance that the event happens on or before that date. For two neighboring deadlines priced P₁ (earlier) and P₂ (later), the chance it happens between them, if it has not happened by the first, is (P₂ − P₁) ÷ (1 − P₁): the gap between the prices divided by the chance that nothing happened first.
A constant hazard is the same chance h every month. Over m months the chance it happens is 1 − (1 − h)m, so a price P for a deadline m months away means h = 1 − (1 − P)1/m. For time decay the calculator keeps the chance per day constant between two deadlines: if nothing happens by a date, a deadline's price becomes 1 − (chance nothing happens by the deadline) ÷ (chance nothing happens by that date). With a single deadline that is 1 − (1 − P)t/T, where T is the time left today and t the time left then.
Later deadlines include the earlier ones, so their prices can only be equal or higher. A later deadline priced below an earlier one is a mispricing: Yes on the later date plus No on the earlier date costs less than $1, pays $1 in every case and $2 if the event falls between the two dates. For the other figures the calculator reads such a price as equal to the earlier one. Check the real asks rather than the midpoints, the fees and that both deadlines resolve on the same rules — see how “by date” markets work.
Related tools: the APY calculator for what a long-dated position earns per year, the arbitrage calculator for mispricings across exchanges, and the combined probability calculator for several events at once.
Put real prices into the calculator: every page below shows current odds, 24-hour moves and the market rules.
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Subtract the earlier price from the later one and divide by what is left of 100: (later − earlier) ÷ (100 − earlier). With 20¢ by the first date and 35¢ by the second, the chance for the time in between, if nothing has happened by the first date, is (35 − 20) ÷ (100 − 20) = 18.8%.
The same chance of the event in every month it stays open. At 10% a month, the chance that it happens within three months is 1 − 0.9 × 0.9 × 0.9 = 27.1%; read backwards, a 27.1% price for a deadline three months away means 10% a month.
Each quiet day uses up part of the window. If the chance per day stays the same, a deadline's price shrinks as it approaches: a 20¢ price falls to about 10.6¢ once half of the time left has passed without the event.
The ladder is inconsistent: whatever happens, Yes on the later deadline plus No on the earlier one pays at least $1, so if the two cost less than $1 together the difference is locked in. Check the real asks, the fees and that both deadlines resolve on the same rules before trading.
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