Market Order
How a Market Order Works
When you place a market buy order, your broker routes it to the exchange or market maker offering the lowest ask price. For a market sell order, it’s matched with the highest bid. The trade executes almost instantly — typically within milliseconds for liquid stocks.
The price you see on your screen at the moment you click “buy” may not be exactly the price you get. By the time your order reaches the exchange, the best available price may have shifted slightly. This difference is called slippage, and it’s the primary risk of market orders.
In highly liquid securities like Apple, SPY, or other large-cap names, slippage on a market order is usually negligible — a penny or two at most. In thinly traded stocks with wide bid-ask spreads, slippage can be significant.
Market Order Example
Suppose a stock is quoted at $50.00 bid / $50.05 ask. Here’s what happens with each type of market order:
| Action | What You Submit | Likely Fill Price | Why |
|---|---|---|---|
| Buy 100 shares | Market buy order | ~$50.05 | You buy at the current ask (the lowest price a seller is offering) |
| Sell 100 shares | Market sell order | ~$50.00 | You sell at the current bid (the highest price a buyer is willing to pay) |
The $0.05 difference between your buy and sell price is the bid-ask spread — and it’s an implicit cost every time you trade. In liquid markets, this cost is minimal. In illiquid markets, it can eat into returns meaningfully.
When to Use a Market Order
Market orders make sense in specific situations:
You need guaranteed execution. If getting the trade done matters more than the exact price — for instance, you want to exit a position during a rapidly moving market — a market order ensures your order fills.
The security is highly liquid. For large-cap stocks and major ETFs with tight spreads and deep volume, the difference between a market order and a limit order is usually negligible. The spread might be a penny, and the trade fills instantly.
You’re trading small quantities. If you’re buying 50 shares of a stock that trades 10 million shares per day, your order won’t move the price. A market order is the most efficient approach.
When to Avoid a Market Order
Market orders become risky when liquidity is thin or conditions are volatile:
Low-volume or illiquid stocks. A penny stock trading 10,000 shares per day with a 5% bid-ask spread can fill your market order at a far worse price than expected. A limit order gives you price control here.
At market open or close. The first and last minutes of trading often see erratic price swings. Market orders placed during these windows are more prone to slippage. Pre-market and after-hours sessions are even worse — liquidity is much thinner outside regular hours.
During high volatility. When the VIX is elevated and prices are swinging wildly, the price you see and the price you get can diverge significantly. The 2010 flash crash is an extreme example — some market orders filled at prices 60% below pre-crash levels.
Large orders relative to volume. If your order represents a meaningful share of daily volume, a market order will “walk the book” — filling at progressively worse prices as it eats through the available orders at each level. Institutional traders use algorithms to break large orders into smaller pieces for exactly this reason.
Market Order vs. Limit Order
These are the two most fundamental order types, and understanding when to use each is a core trading skill:
| Feature | Market Order | Limit Order |
|---|---|---|
| Priority | Speed — fills immediately | Price — fills only at your specified price or better |
| Execution guarantee | Yes (during market hours with available quotes) | No — may not fill if the price never reaches your limit |
| Price guarantee | No — you accept the best available price | Yes — you’ll never pay more (buy) or receive less (sell) than your limit |
| Slippage risk | Higher, especially in illiquid or volatile conditions | None — but you risk not getting filled at all |
| Best for | Liquid securities, small orders, urgent exits | Illiquid securities, larger orders, precise entry/exit levels |
Many experienced traders default to limit orders set at or near the current ask (for buys) or bid (for sells). This gives the speed benefit of a near-immediate fill while capping the worst-case execution price. It’s a hybrid approach that costs nothing extra and eliminates extreme slippage.
Market Orders and Order Flow
When you place a market order through a retail broker, your order typically doesn’t go directly to a stock exchange. Most retail brokers route market orders to market makers or wholesalers (like Citadel Securities or Virtu Financial) who internalize the trade. This practice is called payment for order flow (PFOF) — the market maker pays the broker a small fee in exchange for the right to fill your order.
This system generally works in the retail investor’s favor for small orders — market makers often provide price improvement (filling you at a price slightly better than the quoted bid or ask). But it also means your market order is filled within a system designed to profit from the spread, which is worth understanding.
Key Takeaways
- A market order fills immediately at the best available price — speed is guaranteed, price is not.
- Market orders work well for liquid, large-cap stocks with tight bid-ask spreads.
- Avoid market orders in illiquid stocks, during volatility spikes, and at market open/close.
- Slippage — the gap between expected and actual fill price — is the primary risk.
- When in doubt, use a limit order set near the current market price for the best of both worlds.
Frequently Asked Questions
Can a market order not get filled?
It’s extremely rare during regular trading hours for a listed security. A market order will fill as long as there’s a counterparty willing to trade. However, if a stock is halted (due to news or a circuit breaker), market orders queue and fill at whatever price the stock reopens at — which can be dramatically different from the pre-halt price.
Do market orders cost more in commissions?
No. Most brokers charge the same commission (typically zero for retail accounts) regardless of order type. The cost difference between market and limit orders comes from execution price, not fees.
What’s a marketable limit order?
A limit order priced at or above the current ask (for buys) or at or below the current bid (for sells). It behaves like a market order — filling immediately — but with a price ceiling or floor that prevents extreme fills. Many experienced traders prefer this over pure market orders.
Should I use market orders for ETFs?
For major ETFs like SPY or QQQ during regular hours, market orders are fine. For niche or low-volume ETFs, use limit orders — these ETFs can have wider spreads and less depth, especially at market open when underlying holdings may not all be trading yet.
What happens if I place a market order after hours?
Most brokers won’t execute market orders during extended hours — they require limit orders instead. If you place a market order after the close, it typically queues for the next market open, where it fills at the opening price. This can result in a significant gap from the previous close.