Order types 1: market vs limit orders
A clear guide to market orders and limit orders: how each one works, what it guarantees, and the tradeoff between speed of fill and control over price.
Part of the Market Mechanics: Orders and Execution track on Agenticks. About 8 minutes, written for a intermediate reader.
Once you know you want to buy or sell, you still have to tell the broker how to do it. The order type is that instruction. The two you will meet first, and use most, are the market order and the limit order. They solve the same problem in opposite ways, and picking the wrong one at the wrong moment is a quiet way to give up money you did not have to.
A market order says: fill me right now, at whatever price is currently available. It almost always executes, and it executes fast. That is its whole point. The catch is that you do not choose the price. You take whatever the market is offering at that instant. When you buy at market you usually pay the ask, the lowest price a seller is offering. When you sell at market you usually receive the bid, the highest price a buyer is bidding. The gap between those two is the bid-ask spread, and you cross it the moment you trade. Here is a concrete way to feel it. Say a stock shows a bid of 100.00 and an ask of 100.05. If you send a market buy, you pay 100.05. If you turned around and sold at market a second later, you would get 100.00. Nothing about the stock changed in that second, but you are down five cents per share. That five cents is the spread, and it is the price of demanding an instant fill.
Every order is a trade between speed and price
A market order buys certainty of getting filled and pays for it with price. A limit order buys control of price and pays for it with certainty of getting filled. You cannot have both at once, so the real question is always which one you can afford to give up on this trade.
A limit order says: only fill me at my price or better, never worse. A buy limit fills at your limit price or lower. A sell limit fills at your limit price or higher. That gives you exact control over the price you pay or receive. The tradeoff is that a limit order does not guarantee a fill at all. If the market never trades at your price, your order just sits in the order book, waiting, until it executes, expires, or you cancel it. You traded the certainty of getting in for control over the number. Using the same example, suppose you want to buy that stock but you are not willing to pay the 100.05 ask. You set a buy limit at 100.00. Now one of two things happens. Either a seller comes down to 100.00 and you get the price you wanted, or the stock drifts up and away, your order never fills, and you watch the move from the sidelines. The limit did exactly what it promised: it protected your price. What it could not promise was that the trade would happen.
There is one more reason this choice matters: slippage. Prices move in the time between sending an order and it executing, and a big order can eat through several price levels in the book before it is done. The result is a fill that differs from the price you saw when you clicked. Market orders are the most exposed to this, especially in fast or thin markets where the quote can jump before your order lands. A limit order protects you from a fill worse than your number, but only by accepting that you might not get filled in time.
- Market order
- Fills right now at the best available price
- Limit order
- Fills only at your set price or better
- Slippage
- A fill different from the price you saw
- Bid-ask spread
- The gap you cross between buyers and sellers
Match the order to what the trade needs
If being in the position right now matters more than a few cents, like exiting a fast move, a market order earns its slippage. If the exact price matters more than guaranteed timing, like getting into a calm market at a level you chose, a limit order keeps you disciplined. Neither is better in general. They are tools for different moments.
What does a limit order actually guarantee? A price at least as good as the one you set Correct. A buy limit fills at your price or lower, a sell limit at your price or higher. It controls price, nothing more.
- Market order
- Near-certain to fill, Most exposed to slippage
- Limit order
- Sets the worst price you will accept, May never fill at all
market fill limit price
You can now choose the right order
You know that a market order trades price for a fast, near-certain fill, and a limit order trades a guaranteed fill for control over price. Next you will meet stop and bracket orders, which build on exactly this idea.
Common questions
- What is the difference between a market order and a limit order?
- A market order trades right now at the best price available, so it prioritizes getting filled. A limit order sets the worst price you will accept and only fills at that price or better, so it prioritizes price control over a guaranteed fill.
- Does a limit order guarantee my trade will happen?
- No. A limit order only controls price. If the market never reaches your limit, the order rests unfilled until it executes, expires, or you cancel it.
- Why did my market order fill at a different price than I saw?
- Prices move between the moment you send an order and the moment it executes, and a large order can walk through several price levels. That gap between the expected price and the real fill is called slippage.
Terms defined in this lesson
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