A market order is a request by a trader to execute a transaction as quickly as possible at the best market price. It guarantees order execution but does not guarantee the price at which the order will be executed. Market orders are used when the speed of execution is more important than the price.
To place a market order, enter the amount you want to spend or get and you’ll see the estimated price for your order. This price is calculated from the top of the order book down. For example, say you would like to sell 5 BTC with a market order. There are currently buy orders for 3 BTC at $600 and 4 BTC at $550, which represent the best prices available. Your market order will fulfill the first order completely, giving you $1,800 for 3 BTC, and will fulfill the second order partially, giving you $1,100 for 2 BTC. In total, you’ll receive $2,900, for an average price of $580 per BTC.
Since a market order is executed instantly, it cannot be reversed or canceled. You can place a market order on the Trade page of the CEX.IO website.