Sometimes you buy at market, open your trade history, and find you paid a little more than the price you saw on screen. The exchange didn't make a mistake, and it didn't take a hidden cut either.
Once you see how a market order moves through the order book, it's clear where that gap comes from. This article covers how market orders fill, what slippage is, and when a market order is the right tool and when it isn't.
What a market order is and why the fill differs from the screen price
A market order buys or sells right now without setting a price. The moment you place it, it fills against the opposite side of the order book, starting from the best available price.
That makes the fill almost certain, but the fill price isn't fixed in advance. The price on screen is only the last traded price; it isn't a promise that your order will fill there. We covered how this differs from a limit order, which sets a price and waits, in our limit order article.
How a market buy fills through the order book
A market buy takes the cheapest ask first, and when that level runs out it moves on to the next cheapest. A market sell does the reverse, selling into the highest bid first and working down.
Say a thinly traded coin is at 1.000 USDT and the asks are stacked as below. Buying 2,000 coins at market fills across three levels.
| Ask price | Size available | Spent at this level |
|---|---|---|
| 1.000 USDT | 500 coins | 500 USDT |
| 1.010 USDT | 500 coins | 505 USDT |
| 1.030 USDT | 1,000 coins | 1,030 USDT |
| Total | 2,000 coins | 2,035 USDT |
Buying 2,000 coins cost 2,035 USDT, so the average fill price is 1.0175 USDT. That's 1.75% above the 1.000 USDT shown on screen. Had you bought only 500 coins, the first level would have covered it all and you'd have filled at 1.000 USDT.
When slippage grows: order size and book depth
The gap between the price you expected and the price you actually got is called slippage. It grows or shrinks with how many levels of the book your order eats through.
In a market with a tight, deep book like BTC, most individual orders finish near the first level and the gap is close to zero. On a low-volume coin, a freshly listed coin with a thin book, or in the minutes after big news when price is moving fast, the same amount can skip through several levels.
Before you place the order, open the order book and check whether your size fits within the first few levels. If it doesn't, split the order or use a limit order instead.
Market orders by amount vs. by quantity
Order screens usually let you enter a market order either by amount (total) or by quantity. Enter an amount and the money you spend is fixed while the quantity you get varies; enter a quantity and the quantity is fixed while the money you spend varies.
In the example above, entering 2,035 USDT as the amount gets you 2,000 coins, and entering 2,000 coins as the quantity spends 2,035 USDT. If the book moves before your order fills, the first changes how many coins you get and the second changes how much you pay. Korea's Upbit, for example, takes market buys on its KRW market as a total amount and market sells as a quantity.
Market order fees: the taker rate and the cost under leverage
A market order takes orders that were already resting on the book, so it always fills as a taker. Many exchanges, Binance Futures among them, charge makers less than takers, so the same trade costs a little more in fees when done at market. Exact rates differ by account tier and product, so check the exchange's fee schedule.
With leverage, as in futures, fees and slippage apply to the position size, not to your margin. If the 2,035 USDT position from the example were opened at 10x, the margin would be about 203 USDT, and the 35 USDT of slippage would be about 17% of that margin. The trade starts that far down the moment you enter.
When to use a market order and when a limit order is better
A market order fits when getting filled now matters more than the price. The classic case is a position that hits its stop and needs to be closed quickly. That's also why traders set a stop-market order in advance, which sends a market order once price reaches the stop. We covered how to set the stop price in our leverage article.
For entries that aren't urgent, coins with thin books, and large sizes, a limit order is the better choice. If waiting a few more minutes costs you nothing, there's no reason to pay slippage and the taker fee.
A market order buys speed. You pay for it in slippage and the taker fee.
Market order FAQ
Can I cancel a market order?
It fills the instant you place it, so in practice there's no window to cancel. Double-check the quantity and the buy or sell side before you press the button.
Where can I see the price my market order actually filled at?
Your order history or trade history shows the average fill price. If the order filled across several levels, each level may show up as a separate fill.
Sources
Crypto trading carries a risk of losing your principal.