What is a market order?
Every stop-loss you will ever set becomes a market order the instant it triggers. Understanding what that order does inside the book — and what it costs — is the difference between a planned loss and a surprising one.
What happens inside the book when I send one?
The exchange matches your order against the resting orders on the other side, starting from the best price and moving outward until your full size is filled. If the best level has enough size, you get that price. If not, the remainder fills at the next level, then the next. Your fill is the average across every level you consumed.
Working: 0.05 × $77,500.5 + 0.05 × $77,501.0 = $7,750.075 for 0.10 BTC, so $77,500.75 per coin. On BTC that $0.25 is nothing. Run the same order on a pair where each level holds $500 and the average lands several levels deep.
What does a market order actually cost?
| Cost | Where it comes from | Example on a $5,000 order |
|---|---|---|
| Taker fee | You removed liquidity; the exchange charges its taker rate | 0.05% = $2.50 (typical perps rate as of 2026; check your tier) |
| Half the spread | You crossed from the mid-price to the ask | 0.01% spread → $0.25 |
| Slippage | Your size exceeded the best level | $0 on BTC; $10–$50 on a thin altcoin |
| Total | ~$2.75 on BTC · $12–$52 on a thin pair |
Fee tiers change by exchange and volume; the point is the ranking. On liquid pairs the fee dominates; on thin pairs slippage does.
When should a beginner use a market order?
When execution certainty is the priority: closing a position that is going against you, exiting before an event you do not want to hold through, or entering a liquid pair where the cost is a few cents and a limit order might miss. Protective stops should be stop-market, not stop-limit, for exactly this reason: in a crash a stop-limit can sit unfilled below the price while the market keeps falling.
When is a market order the wrong tool?
On thin pairs, with large size relative to depth, and during the seconds after news when makers have pulled their quotes. In those conditions a market order pays the widest spread of the day plus slippage across many levels. Use a limit order and accept the risk of not filling, or split the order into smaller pieces spaced out so the book can refill between them. And never use a market order to enter a position simply because you are excited — that is the FOMO entry, and it is the most expensive one on the chart.
FAQ
Does a market order always fill? On a liquid pair, effectively yes and within milliseconds. On an illiquid one it fills only as deep as the book goes, so a very large order can fill at absurd prices — exchanges sometimes cap this with price-band limits.
Why did my market order fill at a worse price than shown? Because the size resting at the displayed price was smaller than your order, so the remainder walked to worse levels. That difference is slippage.
Is a stop-loss a market order? A standard stop-loss becomes a market order when the trigger price trades. That is why it fills but does not guarantee the trigger price — and why a stop-limit, which does not, can fail to fill at all.
Practise both order types with no money at risk
The Practice Arena runs at live prices with stops enforced, so you can see what a market fill costs before it is real.
Every key term, one roadmap
The whole slide course — ten free PDF parts, 328 pages.
Market and limit orders are the two halves of one decision: certainty of fill or certainty of price. Lesson 6 — market, limit and stop orders walks through all three types with the stop-market versus stop-limit trap, and take-profit covers the order on the other side of the trade.