Every contract has a price to buy and a lower price to sell. The distance between them is the spread, and it is one of the most overlooked costs in trading an event contract.
The spread is the gap between the highest price a buyer will pay, the best bid, and the lowest price a seller will accept, the best ask. To buy at once you pay the ask, and to sell at once you take the bid, so you cross that gap on the way in and again on the way out. A narrow spread is cheap to trade, a wide spread is expensive, and the size of the spread is shaped by how many people are competing to quote that contract.
Illustrative order book. The best ask is the lowest price a seller will accept and the best bid is the highest price a buyer will pay. The dashed band between 54c and 57c is the spread, where no orders rest. Numbers are an example to show how the book works, not a quote and not a prediction.
A contract does not have a single price. There is a price to buy now, the ask, and a lower price to sell now, the bid. The number you see quoted on a chart is usually the last traded price, which can sit anywhere between the two. The spread is simply the distance between the best bid and the best ask, and it is the first thing to read before you assume a contract is cheap or dear.
To enter a position immediately you pay the ask. To exit immediately you take the bid. That means a round trip crosses the spread twice. If the best bid is fifty four cents and the best ask is fifty seven cents, you buy at fifty seven and could only sell back at fifty four, a three cent loss before anything else happens. The spread is a real cost that comes straight out of any edge you believe you have.
Spreads widen when few people are willing to quote a contract, which is common away from the busiest markets and in the hours after a contract first opens. A wide spread is a warning that the market is thin, that the quoted price may not hold in size, and that getting out later could be costly. A tight spread usually means more competition, though it can widen fast when news arrives.
The spread is not the only cost. A platform may charge a fee per contract or take a portion of each trade, and that adds to the spread you already cross. On Kalshi a taker fee of seven cents times the price times one minus the price applies per contract, per its fee schedule effective February 2026. The true cost of a round trip is the spread plus any fees plus any slippage from thin depth.
Picture a contract quoting a best bid of fifty four cents and a best ask of fifty seven cents. The spread is three cents. Buy one contract at fifty seven and, if nothing else moves, the most you could sell it back for right now is fifty four. That three cent gap is the cost of a round trip before any fee. On a small spread it is a nuisance, on a wide one it can erase the whole reason you took the trade.
Illustrative figures to show the mechanics, not a quote and not a prediction.
The spread exists because buyers and sellers rarely agree on an exact price at the same instant. Someone willing to sell wants a little more than someone willing to buy is offering, and the gap between them is the spread. Market makers and other traders earn part of their return by quoting both sides and capturing that gap, which is why a contract with many competing quotes tends to have a tighter spread than one with few. On a venue that pays liquidity providers, competition is engineered on purpose. Polymarket redistributes a portion of taker fees, reported at roughly 20 to 25 percent depending on the category, to makers through its rebate program, per its fee documentation as of April 2026, and that incentive is one reason its average spread narrowed over time.
For you, the spread is the cost of immediacy. If you want to trade right now, you accept the worse of the two prices, the ask to buy or the bid to sell. If you are willing to wait, you can post your own order inside the spread and let someone else cross it, which can lower your cost but gives up the certainty of trading at once. Every trade is a choice between paying the spread for speed and waiting for a better price with no guarantee of a fill.
This matters most on the contracts where it is easiest to forget. A market that looks active can still carry a wide spread on a particular contract, and a single appealing price at the top of the book can be backed by very little size. Reading the spread, and the size available at each price, tells you whether the number you see is real for the amount you want to trade or only for a tiny order sitting at the front. The order book ladder above shows the point plainly: the ninety five contracts resting at the best ask may fill your first trade cleanly, but a larger order would walk up to fifty eight and fifty nine cents and pay a worse average price.
The spread also changes through the life of a market. It is often widest right after a contract opens, when few participants have arrived, and again around the moment of resolution, when uncertainty spikes or liquidity drains away. A spread that was a single cent in calm conditions can jump to several cents when news breaks, exactly when you might most want to trade. Treat the spread as a live reading of conditions, not a fixed feature of the contract.
The spread is set by the market, but the fee on top of it is set by the platform, and the two together are your real cost. The table shows how a few venues price a trade. Pricing models differ, so read the model column, not only the headline figure.
| Platform | How trading is priced | Headline trading cost | Source date |
|---|---|---|---|
| Kalshi | Central order book; explicit per contract fee on top of the spread | Taker fee 7c times price times (1 minus price) per contract; maker fee 25 percent of that | Fee schedule, eff. Feb 2026 |
| Polymarket | Central limit order book; makers free, takers pay a category fee; maker rebates fund tighter spreads | Taker cap from 0.75 to 1.80 dollars per 100 shares by category; makers pay nothing | Fee docs, as of Apr 2026 |
| Sporttrade | Exchange against other users; no per trade fee, a cut of net profit instead | Reported 2 percent commission on net winnings; nothing taken on losing trades | Reported Jun 2026 |
| Every venue | The spread itself is paid on top of any of the above, on entry and again on exit | Varies live with competition and conditions; widest on thin or newly opened contracts | General |
Methodology: figures are drawn from each platform's published fee schedule or documentation, or from reputable reporting where a platform does not publish a single schedule, and are dated in the final column. Availability differs by region and is not implied by inclusion here. Verify the current schedule before you trade, since fees and spreads change. Sources: Kalshi fee schedule, effective February 2026; Polymarket fee documentation, as of April 2026; reporting on Sporttrade commissions, as of June 2026.
A spread looks the same on every screen, a gap between a buy price and a sell price, but what sits behind it changes from one venue to the next. Knowing the structure helps you read why a spread is tight or wide and what it will cost you to cross. There are broadly three shapes you will meet across the sixteen platforms we cover.
The first is the central order book that posts an explicit fee on top. Kalshi works this way. Buyers and sellers rest orders at named prices, the spread is the gap between the best of each, and a separate fee is charged when you trade. Per the Kalshi fee schedule effective February 2026, the taker fee is seven cents times the price times one minus the price for each contract, and the maker fee is a quarter of that, which means the fee is largest on contracts priced near the middle and smallest on contracts priced near the edges. Here your total cost is easy to add up because the spread and the fee are two clearly separate numbers.
The second is the order book that pays the people who narrow the spread. Polymarket runs a central limit order book where makers, the traders who post resting orders, pay no fee and takers pay a category fee, per its fee documentation as of April 2026. A share of the taker fees, reported at roughly twenty to twenty five percent depending on category, is returned to makers through a rebate program. That design rewards anyone who tightens the spread, and it is part of why the average spread on the venue fell from about four and a half percent in 2023 to roughly one point two percent by late 2025, per market reporting. When a venue subsidizes makers, the spread you cross as a taker tends to be narrower, though the category fee still applies.
The third is the exchange that charges nothing per trade and instead takes a slice of what you win. Sporttrade matches your order against other users rather than a house, and reporting as of June 2026 describes a commission of about two percent on net winnings, with nothing taken on losing trades. On a venue like this there is no per trade fee to add to the spread, so the spread is closer to your whole trading cost on the way in and out, while the commission lands only on profit at the end. None of these models is better or worse in the abstract. Each shifts where the cost falls, and reading the structure tells you which number to watch.
The simplest protection is to look before you act. Check the best bid and the best ask to see the spread, then look at the size resting at the next few price levels to judge whether the quote holds in your size. If the spread is wide or the depth is shallow, a market order is likely to fill worse than the screen suggests, and that is the moment to slow down.
A limit order is the main tool for controlling the spread. By naming the worst price you will accept, you can try to trade inside the spread rather than crossing the whole of it, and you avoid handing the price decision to the book. On a venue that pays makers, posting inside the spread can even earn a rebate rather than pay a fee. The trade off is that a limit order may never fill if the market moves away from your price. That is the honest cost of price control, and there is no order type that removes it.
It also helps to think in round trips, not single trades. A spread you can shrug off on the way in is paid again on the way out, so a strategy that involves trading in and out often is far more exposed to the spread than one that holds to resolution. If you plan to trade frequently, the spread and fees together can quietly become the largest cost you face, larger than any single losing position.
None of this tells you whether a contract is worth buying. The spread describes the cost and the mechanics of trading, not the probability of an outcome or whether a price is fair. We never name a contract to buy or predict a result. Reading the spread well has a humbler purpose, which is to stop you paying more than you meant to and to keep the real cost of a trade in front of you before you commit money to it.
A tight spread is not a signal to trade more, and a deep market can still turn against you. The spread is a cost, not a measure of whether an outcome is likely. Stake only what you can afford to lose, never to chase a loss, and never on borrowed money. If it stops feeling like a free choice, step back. In the United States you can call or text the helpline on 1-800-GAMBLER or visit ncpgambling.org.
Once you can read a spread, the next step is to see how it sits against the fee and the depth on each venue, and which venues are available where you live. Use the reference pages below. We rate and explain, we do not sell, and availability differs by region, so check the legality of a platform for your location before you open an account.
It is the gap between the highest price a buyer will pay, the best bid, and the lowest price a seller will accept, the best ask. You pay the ask to buy at once and take the bid to sell at once, so the spread is the cost of trading immediately.
Because you cross it on the way in and again on the way out. If you buy at the ask and later sell at the bid, the round trip pays the spread both times, before any fee. That is why a wide spread can quietly erase the reason you took a trade.
A wide spread usually means few people are competing to quote that contract, which is common in thin markets and just after a contract opens. More competition tends to tighten the spread, though it can widen fast when news arrives. Average Polymarket spreads narrowed from roughly 4.5 percent in 2023 to about 1.2 percent by late 2025 as more makers competed, per market reporting.
Check the spread and the depth before you trade, consider a limit order to trade inside the spread rather than crossing all of it, and trade less often, since each round trip pays the spread again. A limit order may not fill, which is the trade off for price control.
No. The spread is the gap between buy and sell prices set by the market, while fees are charges the platform adds on top. On Kalshi a taker fee of seven cents times price times one minus price applies per contract, per its fee schedule effective February 2026, while Polymarket makers pay nothing and takers pay a category fee, per its fee documentation as of April 2026. The true cost is the spread plus any fee plus any slippage.
No. The spread describes the cost of trading, not whether an outcome is likely or a price is fair. We never name a contract to buy or predict a result. Reading the spread only helps you control cost.
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