# Market Orders

> A market order buys or sells immediately at the best available price. Learn how it fills, what slippage costs and when a market order is the wrong choice.

Source: https://learn.tradelabsai.com/orders/market-orders/  
Track: Orders and Execution · Level: Beginner · Updated: 2026-10-03  
Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice.  
Cite as: TradeLabs Learn, "Market Orders", https://learn.tradelabsai.com/orders/market-orders/

A market order is an instruction to buy or sell **immediately**, at the best price available right now. It is the simplest order there is and the default on many trading apps. It guarantees that you trade, as long as someone is on the other side, but it does not guarantee the price. Knowing exactly how a market order fills will save you money on every trade you make.

## How a market order fills

A market order trades against orders already waiting in the [[the-order-book-and-market-depth|order book]]:

- A **market buy** takes the lowest ask, then the next lowest, and so on until your size is filled.
- A **market sell** hits the highest bid, then the next highest, until your size is filled.

If your order is small compared with what is available at the best price, you get one fill at the best ask or bid. If it is large, you "walk the book."

**Example: Walking the book**
The asks for a small company stock look like this: 200 shares at $10.05, 300 at $10.08, 500 at $10.15. You send a market order to buy 800 shares.
You get 200 at $10.05, 300 at $10.08 and 300 at $10.15. You pay $8,079 in total, an average of about $10.10 a share, five cents above the best ask you saw on screen. On 800 shares that is $39 more than if everything had filled at $10.05.

The gap between the price you expected and the price you got is called [Slippage](https://learn.tradelabsai.com/markets/slippage/). With market orders in liquid stocks it is usually tiny. In thin markets, fast markets or with large orders, it can be the largest cost of the trade.

## What you always pay: the spread

Even with zero slippage, a market order pays the [Bid-Ask Spread](https://learn.tradelabsai.com/markets/bid-ask-spread/). Buying at the ask and later selling at the bid costs you the full spread on top of any commission. On a stock quoted $49.98 / $50.02, that is 4 cents a share, or 0.08%. On an option quoted $1.90 / $2.10, it is 20 cents, or about 10% of the option's value. Always look at the spread before you send a market order.

## When a market order makes sense

Market orders are the right tool when getting filled matters more than a small difference in price:

1. **Exiting a position that is going wrong fast.** If your plan says get out, getting out is more important than saving two cents.
2. **Highly liquid markets in normal hours.** Large company stocks, major currency pairs and the most traded futures usually have deep books and one tick spreads.
3. **Small orders.** If your order is a fraction of the size shown at the best price, your fill will be at or very close to the quote.
4. **When the opportunity is moving away.** In a genuine breakout, waiting for a limit fill can mean missing the trade entirely.

## When a market order is the wrong choice

- **Thinly traded assets.** Small stocks, obscure tokens and far dated options can have wide gaps between price levels.
- **At the open and close.** Spreads are often widest in the first minutes of the session. The opening price can also differ sharply from the previous close.
- **Around big news.** During earnings, central bank decisions or data releases, liquidity can vanish for seconds and fills can be far from the last price.
- **Outside regular hours.** Extended hours sessions have fewer participants; many brokers only accept limit orders then for this reason.
- **Large orders relative to volume.** Break them up or use limits. See [Market Impact](https://learn.tradelabsai.com/orders/market-impact/).

**Watch out: Market orders when the market is closed**
A market order placed overnight waits for the next open and fills at whatever the first available price is. If the stock gaps 8% on news before the open, your order fills after the gap. If you must place an order while the market is closed, a limit order caps the price.

## Market orders and stops

A regular [[stop-orders|stop order]] becomes a market order when triggered. That is why stop losses sometimes fill below the stop price: once triggered, it takes the best bid available, and in a fast fall that may be several levels lower. If you would rather not trade at all than accept a bad price, a [[stop-limit-orders|stop-limit order]] sets a floor, at the cost of possibly not getting out.

## Protecting yourself while using market orders

- **Check the quote and the size at the best price** right before you click.
- **Trade during liquid hours** whenever possible.
- **Use a marketable limit order instead.** This is a limit order priced at or just through the current ask (for a buy). It fills immediately like a market order in normal conditions but refuses to fill past your limit if the book suddenly thins. Many professionals use this instead of true market orders.
- **Size sensibly.** If your order is larger than what is shown at the best price, consider splitting it.

**Tip: The marketable limit order**
Stock quoted $49.98 / $50.02 and you want in now. Instead of a market buy, send a buy limit at $50.05. In normal conditions you fill at $50.02 immediately. If the price spikes to $50.40 in the moment you click, you are protected: the order waits instead of chasing.

## Market orders in other markets

- **Forex and crypto** platforms usually execute market orders instantly against a dealer or the order book, and slippage shows up mainly around news.
- **Futures** market orders in the most liquid contracts typically fill within a tick of the quote.
- **Prediction markets** such as Polymarket also have order books. A market buy of "Yes" shares takes the cheapest offers first, so a large order in a thin market pays a higher average price per share.

## Key takeaways

- A market order guarantees a fill, not a price.
- You always pay the spread, and large or badly timed orders also pay slippage.
- Use market orders in liquid conditions, or when getting out matters most.
- A marketable limit order gives you speed with a price cap.

Next, learn how to name your own price with [Limit Orders](https://learn.tradelabsai.com/orders/limit-orders/), then compare the two directly in [Market vs Limit Orders](https://learn.tradelabsai.com/orders/market-vs-limit-orders/).

## Frequently asked questions

### Does a market order always fill?

In normal conditions, yes, as long as there are orders on the other side. What is not guaranteed is the price. In a thin or fast market, a market order can fill far from the last price you saw.

### What is slippage on a market order?

Slippage is the difference between the price you expected and the average price you actually got. It happens when your order is larger than the size available at the best price, or when the price moves between your click and the fill.

### Should I use a market order at the open?

Usually not. Spreads are often widest in the first minutes of the session and prices can jump. A limit order, or waiting a few minutes, typically gives a better fill.

## Sources

- U.S. Securities and Exchange Commission, [Market order](https://www.investor.gov/introduction-investing/investing-basics/glossary/market-order)
- U.S. Securities and Exchange Commission, [How stock markets work](https://www.investor.gov/introduction-investing/investing-basics/how-stock-markets-work)

## Continue learning

- Next lesson: [Limit Orders](https://learn.tradelabsai.com/orders/limit-orders/)
- Previous lesson: [Order Types Explained](https://learn.tradelabsai.com/orders/order-types-explained/)
- Related: [Order Types Explained](https://learn.tradelabsai.com/orders/order-types-explained/): Market, limit, stop, stop-limit and trailing stop orders explained with examples. Learn what each order does, when to use it and the mistakes to avoid.
- Related: [Limit Orders](https://learn.tradelabsai.com/orders/limit-orders/): A limit order trades only at your price or better. Learn how buy and sell limits work, why they may not fill, queue priority and how to set a smart limit price.
- Related: [Market vs Limit Orders](https://learn.tradelabsai.com/orders/market-vs-limit-orders/): Market orders fill now at an uncertain price; limit orders fix the price but may not fill. Compare costs, risks and the right situations for each order type.
- Related: [Slippage](https://learn.tradelabsai.com/markets/slippage/): Slippage is the gap between the price you expect and the price you get. Learn what causes it, how to measure it and the practical ways to reduce slippage.
- Related: [Bid-Ask Spread](https://learn.tradelabsai.com/markets/bid-ask-spread/): The bid-ask spread is the gap between the best price to buy and the best price to sell. Learn how to read it, what it costs you and how to pay less of it.
- Related: [Liquidity](https://learn.tradelabsai.com/markets/liquidity/): Liquidity is how easily you can trade without moving the price. Learn the signs of a liquid market, how illiquidity costs you and when liquidity disappears.
- Related: [The Order Book and Market Depth](https://learn.tradelabsai.com/market-structure/the-order-book-and-market-depth/): The order book lists every waiting buy and sell order by price. Learn to read market depth, what imbalances show, spoofing risks and how depth affects fills.