What is slippage on Kalshi?

Slippage on Kalshi is the gap between the price you saw and the average price your order filled at. It happens for two reasons. Your order is bigger than the number of contracts offered at the best price, so the rest fills at worse prices. Or the price moves between the moment you look and the moment your order arrives. Kalshi's own help center defines it the same way: the price you receive on a market order may differ from the price you saw when placing it.

Slippage is the cost nobody lists on a fee schedule, and on a thin market it is bigger than the fee. This page shows where it comes from with a real order book walk, then explains every other number on a Kalshi screen: volume, open interest, portfolio and cash, bid and ask, last price, limit and market orders, Yes and No prices, and payout.

Where slippage comes from

Kalshi runs an order book. Every price on it has a size next to it, which is how many contracts are for sale at that price. The headline price is only the best one. When you buy more than that level holds, your order keeps going to the next price up, and the next, until it is full.

Kalshi's quick order article gives the plainest example. 500 Yes contracts are offered at 10 cents and more are offered at 12 cents. You place an order for 1,000. You buy 500 at 10 and 500 at 12, and your average price is 11 cents. The screen said 10. You paid 10% more than that on the whole order.

A worked example walking the order book

A market shows Yes at 52 cents, the last trade. You want 400 Yes contracts and you send a market order. These are the sellers on the book:

• You pay $218.00 for 400 contracts. The average fill is 54.5 cents.
• Against the best ask of 53 cents, slippage is 1.5 cents a contract, or $6.00.
• Against the 52 cents on the screen, you are 2.5 cents a contract worse, or $10.00.
• The taker fee adds $6.94. Each level pays 0.07 x contracts x price x (1 - price): $1.74, $2.61 and $2.59, rounded up once for the order.
• All in, 400 contracts cost $224.94, or 56.2 cents each on a market that said 52.

Slippage and the fee cost about the same here, $6.00 and $6.94. The difference: you can't trade around the taker fee without resting an order, but the slippage came from one choice, sending 400 contracts into a book with 100 at the top.

Slippage grows with your order size

The same book, with five different order sizes:

Slippage grows faster than size. 250 contracts slip $1.50 and 600 slip $16.50. The first 100 contracts are free of it. The last 150 of a 600 contract order cost 59 cents each, 6 cents above the best ask. Slippage is a tax on impatience, and it climbs fastest on the last contracts you buy.

Slippage hurts most at the edges

One cent of slippage is not the same cost at every price. Measure it against your stake and against what you stand to win.

A longshot buyer who slips from 5 cents to 6 just paid 20% more for the same ticket. A favorite buyer who slips from 95 to 96 just gave away a fifth of the profit. Both ends of the price range are where books are thinnest too, so this is where a market order does the most damage.

Slippage and the spread are different costs

The spread is the gap between the best bid and the best ask. Slippage is what you pay beyond the best price. A one contract market order pays the spread and no slippage. A 600 contract market order pays both.

• Spread: bid 51, ask 53. Buy at 53 and sell right back at 51, and you lose 2 cents a contract with no price move at all.
• Slippage: the extra you pay because your size went past the 53 cent level.
• Fee: the taker fee on top of both, on the way in and again on the way out.

Slippage works on sells the same way, in the other direction. A large sell fills down through lower and lower bids, which is why a cash out returns less than the screen price. The sell side is worked through in how to cash out on Kalshi.

How to read the Kalshi order book

The order book lists every resting order on a market with its price and quantity. A resting order is an offer that did not match right away and is waiting for someone to take it.

• Bid: the highest price a buyer will pay. When you sell at market, you get the bid.
• Ask: the lowest price a seller will accept. When you buy at market, you pay the ask.
• Spread: ask minus bid. A tight spread means cheap trading. A wide one means the market is thin.
• Depth: how many contracts sit at each price. Depth, not the headline price, decides your slippage.

One detail makes Kalshi's book easier once you see it. Yes and No are one market. Kalshi's API returns only bids, one list for Yes and one for No, because each side's ask is the other side's bid turned around: a Yes bid at a price is a No ask at $1.00 minus that price. In Kalshi's own example the best Yes bid is 42 cents and the best No bid is 56 cents. The Yes ask is $1.00 minus 56, so 44 cents, and the spread is 2 cents.

Yes and No prices

The Yes price is the market's chance the event happens, and the No price is the chance it doesn't. Yes at 70 cents reads as 70%. A Yes contract and a No contract on the same market pay $1.00 between them, so the two prices sit near $1.00 together.

They rarely add to exactly $1.00 on the buy buttons, because each button shows an ask. Yes ask 44 plus No ask 58 is $1.02. That 2 cents is the spread, showing up on both sides. Odds, implied probability and payout multiples are covered in reading prediction market odds.

What last price means

The last price is the price of the most recent Yes trade. It tells you what someone paid, not what you can buy or sell at now. On a busy market the last price sits inside the spread and the difference is small. On a quiet market the last trade can be hours old and several cents from the current bid and ask.

Charts and the big percentage on a market card are built from traded prices. Before you size an order, read the bid, the ask and the depth. The last price is the least useful of the four.

What volume means on Kalshi

Volume is the number of contracts that have traded in a market. Kalshi's market data reports it in contracts, with a separate figure for the last 24 hours. A contract is worth $1.00 at most, so the count is not the cash that moved. A volume of 250,000 means 250,000 contracts changed hands. If they traded near 20 cents, about $50,000 in cash moved.

What volume tells you:

• How much attention the market gets. High volume markets have more traders watching and correcting the price.
• Roughly how tight the spread will be. Busy markets attract resting orders.

What it doesn't tell you:

• How much you can trade right now. Volume is past trades. A market can have a million contracts of lifetime volume and 40 contracts at the best ask this minute. Check the depth.
• Which side is winning. Every trade has a buyer and a seller. Volume counts both as one.

Use the 24 hour figure over the lifetime one. A market that traded heavily a month ago and nothing this week will slip you like any other quiet market.

What open interest means on Kalshi

Open interest is the number of contracts currently held in a market. Volume counts every trade forever and only goes up. Open interest goes up when a trade creates new positions and down when traders close them.

What portfolio means on Kalshi

Portfolio is your cash plus the displayed value of your open positions. It is the number at the top of the Portfolio tab, and it moves all day because market prices move. Kalshi's example: 10 contracts at 50 cents show as $5 of positions.

The four points people get wrong:

• The positions number is an estimate. Kalshi says the displayed value of a position is not a price you are sure to sell at. A real sale fills at the bids, with slippage on size. In the mobile app, "Current value" estimates proceeds from the available bids and the estimated sell fee.
• A price move changes portfolio, never cash. Your cash only moves when something happens: a trade, a settlement, a transfer or a fee.
• A resting order is not a position. If a buy you placed isn't in your positions, look in your open orders. It hasn't filled.
• Credit is already inside cash. Credit can't be withdrawn and Kalshi already counts it in the cash figure, so don't add it twice.

The amount you can withdraw can also be lower than your cash, because fresh card and bank deposits are held until they settle. The rules are in how to withdraw from Kalshi.

What payout means on Kalshi

Payout is what you collect if you are right: $1.00 for every contract. It is not your profit. Buy 400 contracts for $218.00 and the payout reads $400.00. Your profit if you win is $400.00 minus the $218.00 cost and the $6.94 fee, or $175.06. Slippage comes straight out of that number: the same 400 contracts at the 53 cent best ask would have left about $6 more.

Market orders on Kalshi

A market order fills right away at the best prices available. Kalshi's app calls it a quick order. You enter a number of contracts or a dollar amount and Kalshi fills it as cheaply as the book allows, across several prices when the top one runs out. The order panel works out the average price and shows it before you submit.

• It always takes liquidity, so it always pays the taker fee.
• It gives you speed and certainty of a fill, and hands the price to the book.
• It is the right tool when the price is moving and being in matters more than a cent.

One fact from Kalshi's API docs is worth knowing. The order endpoint has no market order type. Every order carries a price. A market order is a limit order priced far enough through the book to fill at once, which means you can always choose that price yourself.

Limit orders on Kalshi

A limit order names your price and fills only at that price or better. A buy limit sets the most you will pay. A sell limit sets the least you will accept. It can fill now, later, in part or never, and it can't fill worse than your number. That one rule is the whole cure for slippage.

Kalshi's example: 250 contracts are offered at 31 cents and you place a limit order for 1,000 at 31. You buy 250 at once. The other 750 rest on the book at 31 until a seller takes them. A market order for the same 1,000 would have chased the price up.

How long a limit order lasts is your choice:

• Until the market expires. The default in the app. The unfilled part stays on the book.
• End of day or a custom time. The order cancels itself then.
• Immediate or cancel. It fills what it can at your price right now and cancels the rest. Nothing rests.
• Fill or kill. Available through the API. The whole order fills at once or none of it does.

A limit order priced at or through the best ask fills on arrival and pays the taker fee, because it took liquidity. Only the part that rests and fills later counts as a maker. The fee math for both is in Kalshi fees explained.

How to cut slippage on Kalshi

1. Use limit orders. Set the price at the best ask and you buy everything offered there with zero slippage. Whatever is left rests at your price.
2. Use immediate or cancel when you want speed with a ceiling. Price the limit a cent or two through the best ask. You take the levels you accept, nothing above them, and nothing is left on the book.
3. Size to the book. In the example, 250 contracts slipped $1.50 and 600 slipped $16.50. Read the depth and stop where the price gets silly.
4. Split large orders. Take the top level, let sellers refill it, and take it again. Three orders of 200 beat one order of 600 on most books.
5. Trade when the market is busy. Books are deepest close to the event and during it. A game market at 3am has the same question and a fraction of the depth.
6. Stay out of fast moments with market orders. Right after a score or a data release, resting orders get pulled and the book thins out. A limit order protects you there.
7. Read the average price, not the headline. Kalshi shows the average for your whole order on the panel. If it is more than a cent from the best price, shrink the order or switch to a limit.

Our rule of thumb: when your order is bigger than the size at the best price, you are no longer placing a market order. You are making a decision about every level you touch. Make it on purpose.

See slippage before it happens with Rivo

Rivo is the prediction market terminal for Kalshi, Polymarket, Polymarket US and Gemini, at $9 a week or $15 a month. Your money stays in your own Kalshi account. The order ticket is built around the walk you just read.

• The ticket walks the live book before you send. Type a size and Rivo steps through the Kalshi order book level by level, on Kalshi's own price grid, and shows the average fill, the limit it will send, the fee and the total. The slippage is on the ticket while you can still change the size.
• You set the slippage. A market order from Rivo goes out as an immediate-or-cancel limit at the worst level it walked plus the slippage you chose. It fills inside that price and cancels the rest, so a fast market can't fill you somewhere you never agreed to.
• Limit orders live in the same ticket. A limit trades what crosses on arrival and rests the remainder, and your open orders sit in the portfolio to amend or cancel.
• Paper mode uses the real book. Switch the ticket to Paper and the same order fills against the live Kalshi book with no money. You learn what your size does to a market before it costs anything.
• Bots respect the book too. A live Kalshi bot sizes its order down to the depth inside your slippage limit, sells when the trader it copies sells, and carries a loss limit.
• One portfolio for every venue. Positions, open orders and balances across venues in one place, and you can sell any Kalshi position from it.

Open the terminal and put a size into the ticket to see the walk on a live market, or build a bot and let it do the sizing. The prediction market trading bot page covers how bots enter and exit, alerts tell you when the traders on the Kalshi leaderboard buy, and price alerts tell you when a market reaches the price you wanted, so you can rest a limit and walk away. The full tour is on the prediction market terminal. New to the exchange? Start with how does Kalshi work.

Frequently asked questions