A Polymarket price chart plots the market's chance of Yes over time, so its shape shows how traders' expectations changed. On Nimb, the chart in each market panel shows hourly prices for the timeframe you choose, with a dashed 50% line when the price has crossed even odds.
What does the chart show, in one sentence?
Each point is the outcome's price at the end of an hour, read as a percentage chance, from the start of the timeframe on the left to now on the right.
The chart sits under the reading in the market panel, labelled "Chance of Yes · 7D" (or the outcome's name in a multi-outcome event). The line takes the market's category colour. The top and bottom labels give the highest and lowest values on the chart; the scale zooms to the range the price actually covered, with a small margin. Hover anywhere to see the price and time (UTC) at that hour; a dot marks the latest price. Reading the shape is part of market reading: the level tells you what traders expect, the shape tells you how they got there.
An illustrative 7D chart, as text:
| Time | Chance | Annotation |
|---|---|---|
| 7 days ago | 45% | Start of window |
| 6 days ago, 02:00–14:00 UTC | 45% | Flat line: no trades, last price carried forward |
| 4 days ago | 47% | Slow drift up over two days |
| 2 days ago, 15:00 UTC | 47% → 52% | Crosses the dashed 50% line |
| 1 day ago, 18:00 UTC | 52% → 41% | Step down of 11 points in one hour: likely news |
| Now | 41% | End dot |
What does the dashed line at 50% mean?
It marks even odds, the point where the market flips from "more likely No" to "more likely Yes". It is the only reference line Nimb draws, and it appears only when the chart's range crosses 50%. If the price stayed between 60% and 75% all week, there is no line, because there is nothing to cross. This follows Nimb's design system: one reference, drawn only when it means something.
Crossing 50% matters for headlines ("now the favourite") more than for money: a move from 48% to 52% is 4 points, the same as 70% to 74%.
How do you tell a news jump from a drift?
| Shape | Looks like | Usually means | Check |
|---|---|---|---|
| Jump | Near-vertical step within an hour or two | News, a result or an official announcement | Find the source. Look for a matching bar in money flow. |
| Drift | Steady slope over days | Opinion shifting, polls, slow information | Is the volume steady, or is the drift made of a few small trades? |
| Spike and revert | Up and straight back | A large order hitting a thin book, or a rumour denied | Liquidity in the book; the "Thin order book" check |
| Flat line | Horizontal for hours | No trades in that time | Volume for the timeframe; is the price stale? |
| Staircase to 0% or 100% | Steps towards the end of the scale | Outcome becoming settled | Resolution date and rules |
Why is the line flat for hours?
Because nobody traded, or the price did not change. Nimb builds the chart from Polymarket's hourly price history. Where an hour has no new price, Nimb carries the last known price forward until the next one. Nimb's own tests measured how often this happens: 69% of hourly price changes and 43% of 12-hour changes in its snapshot were exactly zero. A flat stretch is therefore often a stale price, not a stable one. The real price would only show when someone next traded, and it can open well away from the line.
What is an unusual move?
Nimb calls a move unusual when the last 24 hours moved the price by at least 2× a typical day for that market. "A typical day" is the standard deviation of the market's 24-hour changes over the past 30 days. The check runs in the "Before you trade" box:
| Market | Typical day | Last 24 hours | Multiple | Nimb says |
|---|---|---|---|---|
| Quiet policy market | 1.5 pts | +4.0 pts | 2.7× | "Moved +4.0 points in 24 hours, 2.7× a typical day. Unusual moves often follow news: check what happened before you follow it." (highlighted) |
| Busy crypto price market | 5.0 pts | +4.0 pts | 0.8× | "Moved +4.0 points in 24 hours, within a normal day for this market." |
| Any market | under 1 pt | "Flat over the last 24 hours." |
The same 4 points is news in one market and noise in another. On the map, the 12 biggest movers over the timeframe pulse, if they moved at least 1.5 points. More in Before you trade checks.
Which timeframe should I use?
| Timeframe | Chart covers | Good for | Watch out for |
|---|---|---|---|
| 1H, 12H, 24H | Up to 24 hourly points | What moved today; reacting to news | Few points; one trade can dominate |
| 3D, 7D | 72 or 168 hourly points | The week's story; drift vs jump | Weekend gaps and flat stretches |
| 30D | 720 hourly points | Trend and the market's normal range | Old moves that no longer matter |
For market reading, start on 7D, then check 24H for anything recent and 30D for context. The timeframe also changes the points figure beside the chance and the volume rows. See timeframes.
What can a price chart not tell you?
- Why it moved. The chart shows when; the news is elsewhere.
- How much money moved it. A 10-point jump can be $200 in a thin book. Read the chart next to money flow and volume.
- Moves inside the hour. Hourly points hide spikes that reverted within the hour. The live chance at the top of the panel updates in seconds; the chart history does not.
- The future. Trends in prediction markets do not have to continue; a price at 41% is the market's current estimate, and a past slope is not a forecast.
Back to all six checks: how to read a market.
From reading to execution
A chart is one part of reading the market. If it shows a jump, find the news before you act on it; if it shows a flat line, treat the price as possibly stale. Then use the order ticket, which prices your order from the live chance rather than the chart.
Last reviewed 2026-11-07 · Data from Polymarket · Not financial advice · Nimb is not affiliated with Polymarket.