What is a Market Order?
A market order is an instruction to buy or sell a security immediately at the best available current price — execution is nearly guaranteed, but the exact price is not.
A market order is the simplest and most common type of stock order. It instructs your brokerage to buy or sell a security immediately at the best available price in the market. When you place a market order, you're prioritizing speed of execution over price control — you'll get filled right away, but you may not know the exact price until after the trade executes.
For large, liquid stocks like those in the S&P 500, the difference between what you expect to pay and what you actually pay is usually negligible — often just a cent or two. But for thinly traded or volatile securities, market orders can execute at prices significantly different from what you anticipated.
How Market Orders Work
When you place a market order to buy 100 shares of a stock:
- Your order is routed to the exchange
- It matches with the lowest available ask price (the price sellers are willing to accept)
- The trade executes immediately or nearly so
- You receive a trade confirmation showing the actual execution price
For sell market orders, the reverse happens — your order matches with the highest available bid price.
Market Order vs. Limit Order
| Market Order | Limit Order | |
|---|---|---|
| Execution | Immediate | Only at your specified price or better |
| Price certainty | None | Yes — won't fill above/below your price |
| Speed | Fastest | Can take time or never fill |
| Best use case | Liquid stocks; when entry speed matters | Volatile stocks; when price matters more than speed |
Slippage
Slippage is the difference between the expected price of a trade and the actual execution price. It happens when:
- The market moves between the time you click "buy" and when the order executes
- The stock is thinly traded and there aren't enough sellers (or buyers) at the expected price
- You're placing a large order that consumes multiple price levels in the order book
For a day trader executing dozens of trades, slippage can meaningfully erode profits. For a long-term investor buying a broad ETF with a single annual purchase, it's rarely a concern.
When to Use a Market Order
Market orders make the most sense when:
- You're buying a highly liquid stock or ETF — The bid-ask spread is tight and slippage will be minimal
- Speed of execution matters — If you want to get in or out of a position quickly
- You're making a small purchase — The absolute dollar difference in price is unlikely to be meaningful
Limit orders are generally preferred when trading in volatile conditions, thinly traded securities, or when you have a specific target price in mind. For most routine long-term investing in broad index funds or major stocks, market orders work fine during normal trading hours.
Avoid Market Orders After Hours and at Open
Pre-market and after-hours trading tends to be less liquid, with wider bid-ask spreads. Market orders placed during extended hours — or that execute in the first few minutes after the 9:30 AM open — can experience more slippage due to thinner liquidity and wider spreads. Many experienced investors prefer to avoid market orders in these windows.