Explainer · Risk Management
Stop-loss orders: what they do and what they can't
A stop-loss order is an instruction to get out once the price reaches a level you chose in advance. It is useful, but it is a trigger, not a guarantee, and the price you actually get can be worse.
Quick answer
A stop-loss order tells your broker to sell (or buy) once the price reaches your stop price. When that happens it becomes a market order, so the fill can be significantly worse than the stop, especially in fast markets [1]. It limits planned losses; it does not cap them.
Key points
- The SEC treats "stop order" and "stop-loss order" as the same thing [1].
- Once triggered, a stop becomes a market order and fills at the next available price [1].
- A stop price is not a guaranteed execution price [2].
- A stop-limit order controls the price but may not fill at all [1].
- Set the stop where your trade idea is wrong, then size the position from that distance.
On this page
What is a stop-loss order?#
A stop order, also called a stop-loss order, is an order to buy or sell once the price reaches a level you specify, called the stop price [1]. FINRA gives the same definition: an order to buy or sell once the stock reaches a specified price [2].
If you own something, you place a sell stop below the current price. If the price falls to your stop, the order fires and you sell. If you are short, you place a buy stop above the current price. Either way, the point is to decide your exit while you are calm, before the market tests your nerve. Our glossary has a short stop loss meaning if you need the one-line version.
What happens when your stop is triggered?#
When the stop price is reached, a stop order becomes a market order [1]. A market order is filled at the best price available at that moment, and the SEC warns that this price can deviate significantly from the stop price [1].
FINRA's example: if your floor for a share is $50, the sell stop becomes a market order when the share hits $50. If the market is moving fast, you could receive less, potentially significantly less, than $50 per share by the time the order is executed [2]. The difference between the price you expected and the price you got is called slippage. If you are new to order types, start with our guide to market vs limit order.
How do stop, stop-limit and trailing stop orders differ?#
| Order | What triggers it | What happens next | Main risk |
|---|---|---|---|
| Stop (stop-loss) | Price reaches your stop price | Becomes a market order | Fill can be far from the stop |
| Stop-limit | Price reaches your stop price | Becomes a limit order at your limit price | May never fill if the price moves past the limit |
| Trailing stop | Price moves a set amount or percentage against you from its best level | Becomes a market order (or a limit order for a trailing stop-limit) | Same fill risk as a stop; can trigger on a brief dip |
Definitions from the SEC's investor bulletin on stop, stop-limit and trailing stop orders [1].
A stop-limit order combines a stop order and a limit order [1]. After the trigger, it will only fill at your limit price or better. That removes the risk of a terrible fill and replaces it with a different one: if the price moves away from your limit, the order may not be executed at all [1], and you are still holding a losing position.
A trailing stop has no fixed stop price. Instead, the stop sits a defined percentage or dollar amount away from the market price [1] and follows the price as it moves in your favour, but never moves back.
- Buy at $20
In the SEC's example, you buy XYZ at $20 a share [1].
- Add a $1 trailing stop at $22
XYZ rises to $22 and you place a trailing stop $1 below the market, so the stop starts at $21 (calculated).
- The stop follows the price up
XYZ peaks at $24. The stop trails $1 behind and is now at $23 (calculated).
- The price falls back and the stop fires
When XYZ falls to $23, the order triggers and the shares are sold [1]. At a $23 fill, that is a $3 gain per share, 15% on the $20 entry (calculated). In a fast market the fill could be lower.
How do you size a trade around a stop?#
The stop and the position size are one decision. First decide where your reason for the trade would be proven wrong and put the stop there. Then decide how much you are prepared to lose, and divide that amount by the distance to the stop. Our guide to position sizing explains the formula in full.
The regulator guidance we cite gives no rule for where to place a stop, and no fixed percentage below the entry. That is your judgement, and it should come from the trade idea, not from how many shares you would like to buy.
- Amount at risk
- $801% of $8,000, calculated
- Distance to the stop
- $3 per shareentry $40, stop $37, calculated
- Position size
- 26 shares$80 / $3 = 26.67, rounded down, calculated
- Planned loss if filled at $37
- $78 (0.98% of the account)calculated
| Fill price | Loss | Share of the $8,000 account |
|---|---|---|
| $37.00 | $78 | 0.98% |
| $36.50 | $91 | 1.14% |
| $36.00 | $104 | 1.30% |
| $35.00 | $130 | 1.63% |
| $34.00 | $156 | 1.95% |
A triggered stop fills at the next available price, which can be well below the stop [2]. Spreads and commissions are not included.
Can a short-lived dip trigger your stop?#
Yes. The SEC notes that a stop order may be triggered by a short-term, intraday price move and fill at a price you would not have chosen [1]. FINRA devotes a section of its guidance to the same warning: short-lived, dramatic price changes might trigger your stop order [2].
This creates a real trade-off. A stop very close to the entry keeps each planned loss small, but it is more likely to be hit by an ordinary wobble, and then the price may recover without you. A stop further away is triggered less often, but your position must be smaller to keep the same amount at risk. There is no free option here: you are choosing which kind of disappointment you would rather accept.
Do stop-loss rules improve trading results?#
Not automatically. Andrew Lo and Kathryn Kaminski studied stop-loss rules, defined as policies that cut exposure after cumulative losses reach a threshold, in a 2014 paper in the Journal of Financial Markets [3]. Their result is more nuanced than either camp of traders likes to admit.
If prices follow a random walk, meaning each day's return is independent of the last, they show that a stop-loss rule always lowers expected return [3]. You pay for the protection. Using daily US index futures prices from January 1993 to November 2011, they found that, when losses were checked over longer intervals, some stop-loss policies could raise expected return while substantially reducing volatility [3]. In one calibration, a monthly stop-loss rule added 1.5% to return and cut volatility by 5% [3]. That is one setup on one market, not a general expectation.
The practical lesson for a beginner: use a stop to cap how much one mistake can cost and to keep losses small enough to recover from (see drawdown recovery). Do not expect it to turn a losing approach into a winning one.
Mistakes beginners make with stop-loss orders#
- Treating the stop price as the exit price
Planning as if every stop fills exactly at its level. Build the plan around the possibility of a worse fill [2].
- Moving the stop further away as the price approaches
This turns a planned small loss into an unplanned large one. Decide the stop before the trade and leave it, or move it only in the direction that reduces risk.
- Choosing the stop to fit a position you already want
Squeezing the stop closer so you can buy more shares. The stop should come from the trade idea; the size follows from it.
- Using a stop-limit and forgetting it
A stop-limit can be skipped entirely in a fast fall [1]. If you use one, watch the position or have a plan for when it does not fill.
- Not placing a stop at all
Telling yourself you will sell "if it gets bad". Without a level written down in advance, the decision gets made under stress, when it is hardest.
Frequently asked questions#
Does a stop-loss order guarantee my maximum loss?
No. A triggered stop becomes a market order, and FINRA states that stop prices are not guaranteed execution prices [2]. In a fast market the fill can be significantly worse than the stop.
Where should I put my stop-loss?
Where the reason for your trade would be proven wrong. The regulator guidance we cite gives no placement rule and no fixed percentage. Once the stop is set, calculate the size so the loss at the stop fits your plan.
Is a stop-limit order safer than a stop order?
It swaps one risk for another. It will not sell below your limit, but it may not sell at all if the price moves past the limit [1], leaving you in a falling position.
Should I move my stop once the trade is in profit?
Moving a stop in your favour reduces risk; that is what a trailing stop does automatically [1]. Moving it further away to avoid being stopped out increases risk and defeats the purpose.
The bottom line#
A stop-loss order is a decision made in advance about when you will admit a trade is wrong. Use it, but plan for the fill to be worse than the stop, understand that a stop-limit can fail to fill, and size every position from the distance to the stop. Try your numbers with our position sizing guide, and read the risk disclosure before trading anything with leverage.
Sources
Education only. This page is not investment, tax or legal advice. Trading and crypto can lose you money. See our risk disclosure.
