What is slippage on Polymarket?
Last updated July 2026 · The Cent Signals desk
The short answer
Slippage on Polymarket is the gap between the price quoted when an order is submitted and the average price it actually fills at. An immediate order consumes the cheapest resting offers first and works up the book, so an order larger than the top level settles at a blended, less favourable price. Thin books widen that gap. Cent Signals is a free, independent desk that tracks Polymarket activity and explains how prediction markets price probability, not trading advice.
Why a fill price and a quoted price are different numbers
Polymarket matches orders on a central limit order book, described in detail in what is a Polymarket order book. The quoted price on a market page is the best resting offer, which is one price level with one finite size behind it. An order for more than that size does not stop there. It clears the best level, moves to the next, and keeps going until the requested amount is met or the price bound on the order is reached. The fill that comes back is the weighted average of every level it touched.
That average is the real transaction price, and slippage is the distance between it and the price displayed a moment earlier. Nobody collects it and it is not a fee. It is arithmetic that follows from the shape of the book, which is why the same order size produces a rounding error in one market and a completely different price in another on the same afternoon.
What three live Polymarket books looked like on July 26, 2026
Slippage is measurable in advance, because Polymarket publishes the full order book through its public CLOB API. We read the YES book for three markets on July 26, 2026 and walked the resting ask levels in price order to derive the average fill price for a given notional size. The figures below are our own calculation from that snapshot of the books, not a Polymarket-published statistic.
| YES book, as of July 26, 2026 | Democratic Senate control, 2026 | J.D. Vance, 2028 nomination | Russia nuclear test by Dec 31 |
|---|---|---|---|
| Best ask | 44.0c | 42.9c | 11.0c |
| Ask notional within 1c of the touch | $103,138 | $14,126 | $62 |
| Ask notional within 5c of the touch | $136,251 | $91,172 | $105 |
| Average fill on $1,000 | 44.0c, no measurable slippage | 42.9c, no measurable slippage | 35.2c, 220 percent above the quote |
| Average fill on $10,000 | 44.0c, no measurable slippage | 43.3c, 1.0 percent above the quote | 61.9c, 463 percent above the quote |
| Average fill on $50,000 | 44.0c, no measurable slippage | 44.4c, 3.6 percent above the quote | 81.4c, 640 percent above the quote |
The third column is the one worth sitting with. The Russia nuclear test market carried a headline liquidity figure near $13,000 and a tidy looking 11 cent quote, and still had only about $62 of asks within a cent of that quote. Its top level was 400 shares, worth $44. A thousand dollars of demand had nowhere to go but up the book, which is how the arithmetic lands on a 35 cent average against an 11 cent screen price. By contrast the Democratic Senate control market absorbed a modelled $50,000 without moving off 44 cents at all.
Those extreme percentages describe the raw shape of the book rather than a fill anyone would actually receive, because Polymarket's market order types carry a price bound that would stop an order long before it reached 81 cents. They are still the honest measure of how little size sits behind a thin quote.
How thin is a typical market?
Across the 400 markets in our July 24, 2026 snapshot, the median headline liquidity figure was about $62,300. A quarter of the markets sat below roughly $25,300, and 11 percent carried under $10,000. At the other end the deepest market in the set showed about $2.7 million. The distribution is heavily skewed: a small number of flagship markets hold most of the resting capital and the long tail holds very little. The same pattern, read from a different angle, is set out in how order book depth varies by market size.
A headline liquidity figure is a useful proxy and a poor substitute. It totals the book at any distance from the current price, so it counts an order sitting at 90 cents in a market quoted at 11 cents just as readily as one sitting at the touch. The Russia market above is the clean demonstration: about $13,000 of published liquidity, about $62 of it within a cent of the price on the screen. The difference between the two figures is exactly the space where slippage lives, and it is the reason volume and liquidity both need reading with care.
Order types and how far an order can walk
Polymarket's documentation describes limit orders with two lifetimes, good till cancelled and good till date, and market orders with two fill strategies, fill and kill and fill or kill. Every one of them carries a price bound: a maximum price stops a buy from crossing higher, a minimum price stops a sell from crossing lower, and a market buy can also carry a maximum total spend that caps the outlay including fees. Those bounds are what convert an unbounded walk up the book into a partial fill or a rejection.
| Attribute | Market order, fill and kill | Market order, fill or kill | Limit order, GTC or GTD |
|---|---|---|---|
| How it meets the book | Takes the best resting prices immediately and cancels any unfilled remainder | Executes in full against resting prices or does not execute at all | Rests on the book at a stated price and waits for someone to cross it |
| Exposure to slippage | Yes, the filled part can span several price levels | Yes, the whole size fills at a blended price when it fills | None, the stated price is the worst price it can fill at |
| Price certainty | Bounded by the maximum price on a buy or minimum on a sell | Bounded the same way, and rejected outright if the bound is breached | Exact |
| Fill certainty | Partial fills are normal | All or nothing | May never fill |
| Fee side (as of 2026) | Taker, pays the category taker fee | Taker, pays the category taker fee | Maker while it rests, not charged the taker fee |
| Minimum size and increments | Set per market by min_order_size and tick_size in the public API | Set per market by min_order_size and tick_size in the public API | Set per market by min_order_size and tick_size in the public API |
The table sets out mechanics, not a ranking. A resting limit order removes slippage and adds the possibility of never filling, and the two immediate types trade that certainty away for a fill. Which of those properties matters is a question about a participant's own situation, and this desk does not answer it.
Slippage, the spread, and fees are three separate costs
They are routinely collapsed into one number in coverage of the platform, and they behave differently. The spread is the gap between the best bid and the best ask, and it applies to the very first share transacted. Slippage only starts once an order exceeds the size at that best price. The taker fee is a Polymarket charge, applied as of 2026 to orders that remove liquidity, scaled by category and by how close the share price sits to 50 cents, and detailed in Polymarket fees explained. Maker orders, the resting quotes that supply the book, are not charged it.
One consequence follows directly from the table above: the same market can look cheap on spread and expensive on depth. A one cent spread says something about the distance between the two best quotes and nothing at all about the size behind them. Both the Vance market and the Russia market quoted spreads of a couple of cents or less on July 26, 2026, and the size behind those quotes differed by more than two orders of magnitude.
Reading a Polymarket price with depth in mind
A quoted price is a statement about the last increment of size, not about the market as a whole. In a deep market the two are close enough that the distinction rarely matters. In a long-tail market they can be entirely different claims, and the published probability implied by an 11 cent quote is being set by a few hundred dollars of resting orders. That is context worth carrying into how to read implied probability, because a price supported by $62 of depth and a price supported by $103,000 of depth are not equally informative even when they look identical on a chart.
Every market page on this site carries the volume and liquidity that Polymarket publishes, and the markets index lists what we currently track. The glossary defines each term as this desk uses it, and the methodology page sets out where the numbers come from and how often they refresh. The order book measurements on this page were taken once, on the date stated, and books change continuously.
Frequently asked questions
What is slippage on Polymarket?
Slippage is the difference between the price quoted at the top of the order book and the average price an order actually fills at. Polymarket runs a central limit order book, so an order that is larger than the size resting at the best price consumes that level and then the next one up, producing a blended fill. The wider the gap between resting price levels, the larger the slippage on a given order size.
How much slippage is there on a Polymarket market?
It depends entirely on the depth of that market's book, not on the platform. Reading three live Polymarket books on July 26, 2026, the Democratic Senate control market held about $103,000 of asks within one cent of the touch, so a $50,000 order would have filled at the quoted 44 cents with no measurable slippage. The J.D. Vance 2028 nomination market held about $14,100 within one cent, where the same $50,000 order would have averaged about 44.4 cents against a 42.9 cent quote, roughly 3.6 percent worse. A market on whether Russia tests a nuclear weapon by December 31, 2026 held about $62 within one cent.
What is the difference between slippage and the spread on Polymarket?
The spread is the gap between the best bid and the best ask, and it is a cost paid on any size, including the smallest order. Slippage is what accrues on top of the spread once an order is bigger than the size available at the best price. A market can show a one cent spread and still produce heavy slippage if only a few hundred dollars rest at that best price.
Does Polymarket charge a fee for slippage?
No. Slippage is not a fee and no one collects it: it is the arithmetic of filling against progressively worse resting orders. Polymarket separately applies a taker fee, as of 2026, to orders that remove liquidity from the book, sized by category and largest near a 50 cent share price, while maker orders that add liquidity are not charged it. Slippage, the spread, and the taker fee are three distinct costs that stack.
How can slippage be measured before an order is placed?
By reading the resting order book rather than the headline liquidity number. Polymarket's public CLOB API returns every price level and size for a market, which is enough to compute the average fill price for any notional amount by walking the levels in order. The figures on this page were produced that way. A headline liquidity figure counts the whole book at any distance from the current price, so it can be large while the size near the touch is small.
Do limit orders have slippage on Polymarket?
A resting limit order fills at its stated price or better, so it carries no slippage, though it carries the risk of never filling at all. Polymarket's documented market order types work differently: a fill and kill order takes what is available immediately and cancels the remainder, while a fill or kill order executes in full or not at all. Both accept a maximum price for buys and a minimum for sells, and market buys also accept a maximum total spend, which caps how far an order can walk the book.
Related reading
This explainer is editorial reference about publicly available prediction-market data. It is not financial advice, a tip, or a recommendation to take any position, and Cent Signals does not facilitate trades. The order book figures were computed by this desk from Polymarket's public CLOB API on July 26, 2026, and the distribution figures come from our July 24, 2026 snapshot; for how that data is collected, see the methodology page.