A market order is an instruction to buy or sell a stock (or other security) immediately at the best available price. It prioritizes speed over price, meaning your trade will almost certainly go through, but you won’t know the exact price until it executes. This makes it the simplest and most common order type, but it comes with trade-offs worth understanding before you use one.
How a Market Order Works
When you place a market order during regular trading hours (9:30 a.m. to 4:00 p.m. Eastern Time), your broker sends it to the market, where it gets filled at or near the current price. If you’re buying, you’ll pay close to the current ask price, which is the lowest price a seller is willing to accept. If you’re selling, you’ll receive close to the current bid price, which is the highest price a buyer is willing to pay.
The key word is “close to.” The price you see quoted on your screen is the last traded price, not necessarily the price you’ll get. Between the moment you click “buy” and the moment your order actually executes, the price can shift. For heavily traded stocks like those in the S&P 500, that shift is usually negligible, maybe a penny or two per share. For thinly traded stocks, the gap can be much larger.
The Bid-Ask Spread as a Built-In Cost
Every stock has two prices at any given moment: the bid (what buyers are offering) and the ask (what sellers want). The gap between them is the bid-ask spread, and it functions as a transaction cost baked into every market order you place. If a stock has a bid of $50.00 and an ask of $50.05, buying at the ask and immediately selling at the bid would cost you $0.05 per share, even if the stock’s price hasn’t moved.
For large, liquid stocks, the spread is often just a penny or two. For smaller or less actively traded securities, spreads can be much wider, sometimes $0.10, $0.25, or more per share. That cost matters, especially if you’re trading frequently or placing large orders. This is one reason many active traders prefer limit orders, which let you specify the price you’re willing to pay rather than accepting whatever the market gives you.
Slippage: When Prices Move Against You
Slippage is the difference between the price you expected and the price your order actually fills at. It happens most often in two situations: high volatility and low liquidity.
During volatile periods, such as right after an earnings announcement or during a broader market selloff, prices can change in milliseconds. You might see a stock quoted at $45.00 and submit a market order, but by the time it reaches the exchange, the price has already moved to $45.30. That $0.30 gap is slippage, and it works against you whether you’re buying or selling.
Low liquidity creates a similar problem from a different angle. If you want to buy 5,000 shares but only 500 are available at the current ask price, the remaining 4,500 shares will fill at progressively higher prices as your order eats through the available supply. This is why large orders in thinly traded stocks can push the price significantly in the wrong direction. The same effect happens in reverse when selling a large position into a thin market.
When a Market Order Makes Sense
Market orders work best when getting the trade done matters more than getting a specific price. A few common scenarios:
- Highly liquid stocks with tight spreads. If you’re buying shares of a widely traded company with millions of shares changing hands daily, the spread is tiny and slippage is minimal. The convenience of instant execution outweighs the fraction-of-a-penny cost.
- Urgent exits. If you need to close a position quickly because the market is moving against you, waiting for a limit order to fill could cost you more than the slippage on a market order.
- Small orders in stable markets. Buying 50 shares of a blue-chip stock during a calm trading day? The price difference between a market order and a limit order will likely be negligible.
Market orders are less ideal when you’re trading volatile stocks, placing large orders relative to the stock’s daily volume, or working with a security that has a wide bid-ask spread. In those cases, a limit order gives you price control at the cost of possibly not getting filled at all.
Restrictions During Extended Hours
Most brokerages do not allow market orders during pre-market or after-hours trading sessions. These sessions have far fewer participants, which means lower volume, wider spreads, and less reliable pricing. Prices may come from only one or two electronic networks rather than the multiple exchanges and market makers active during regular hours.
To protect investors from extreme price swings in these thin markets, brokerages typically require limit orders during extended hours. If you try to place a market order before 9:30 a.m. or after 4:00 p.m. Eastern, your broker will likely reject it or prompt you to convert it to a limit order.
Market Orders vs. Limit Orders
The core trade-off is simple. A market order guarantees execution but not price. A limit order guarantees price but not execution. If you set a limit order to buy at $50.00 and the stock never dips to that price, your order sits unfilled. A market order placed at the same moment would have gone through immediately, though possibly at $50.10 or $50.25.
For long-term investors buying and holding, market orders on liquid stocks are perfectly reasonable. The few cents of potential slippage won’t meaningfully affect a position you plan to hold for years. For short-term traders, day traders, or anyone working with volatile or illiquid securities, limit orders offer the price precision that can make or break a strategy. Neither order type is universally better; the right choice depends on what you’re trading, how much you’re trading, and how urgently you need the trade to happen.