What is a stop loss?
Written by an ex-institutional trader. What a stop loss is, shown with a diagram, why it is the most important risk tool you have, where to place one, how a trailing stop works, and the mistakes that defeat the point of using one.
Direct answer
A stop loss is an order that automatically closes a trade at a set price to cap your loss if the market moves against you. You place it when you open a position: for a long trade, below your entry; for a short, above. If price reaches that level, the trade closes at market, limiting the damage to a known amount you decided in advance. It is the single most important risk-management tool a trader has.
The stop loss is what lets you control risk before emotion takes over. By defining your maximum loss up front, you can size the position correctly and walk away knowing the worst case. Where you place it should be driven by the chart, beyond a support level or a recent swing, not by how much you are willing to lose, with the position size adjusted to fit. Trading without a stop is the fastest route to the kind of large loss that ends accounts.
What a stop loss is
A stop loss is an order that automatically closes a trade at a set price to cap your loss if the market moves against you. You place it at the moment you open a position, and it sits in the market waiting. For a buy (long) trade, the stop is below your entry; for a sell (short) trade, above it. If price reaches that level, the trade closes, limiting the loss to an amount you chose in advance.
It is the single most important risk-management tool a trader has, because it converts an open-ended risk into a known, fixed one. Without a stop, a losing trade can run as far as the market takes it, and the large losses that wipe out accounts almost always come from trades that had no stop in place.
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How it works
Picture a long trade. You buy at your entry, and you place a stop loss below it. The distance between the two, the stop distance, is your risk on the trade. If price falls to the stop, the trade closes and the loss is capped at that distance, no matter how much further the market drops.
Because the maximum loss is known before you enter, you can size the position so that loss equals only a small, pre-decided percentage of your account. That is the link between the stop loss and position sizing: the stop sets the risk per unit, and the size sets how many units, so the total risk lands exactly where you want it.
Where to place one
The most common beginner error is placing the stop based on how much they are willing to lose. That is backwards. The stop should sit at a price that proves the trade idea wrong, and the position size should then be adjusted to fit the risk.
- For a long: just below the support level, swing low, or moving average you are trading from, with a small buffer for noise.
- For a short: just above the equivalent resistance or swing high.
The skill is balance. Too tight, right on an obvious level, and normal volatility stops you out before the move happens. Too wide, and the loss is larger than it needs to be. Place it where being hit genuinely means you were wrong, then size the trade to keep that loss small.
Trailing stops
A trailing stop is a stop loss that follows price in your favour but never moves against you. On a long, as price rises, the trailing stop ratchets up behind it at a set distance; if price then falls by that distance, the trade closes. It lets a winner run while locking in more and more of the gain, and removes the temptation to bank profit too early.
The trade-off is that a normal pullback within a trend can trigger a trailing stop before a larger move resumes. A trailing stop set too tight gets shaken out; set sensibly, it is a clean way to manage a trade that is working without having to watch it constantly.
Common mistakes
The ways a stop loss gets misused:
- Trading without one. The cardinal sin. One stop-less trade in a bad move can undo months of gains.
- Sizing the stop to your wallet, not the chart. Place the stop where the idea is wrong, then size the trade, not the other way round.
- Moving the stop further away. Widening a stop to avoid being hit turns a small planned loss into a large unplanned one. Move stops only in your favour.
- Setting it too tight. A stop right on the level gets clipped by noise. Leave a buffer.
A stop loss on every trade, placed by the chart and respected once set, is the habit that keeps you in the game. Pair it with position sizing, the drawdown calculator, and an understanding of support and resistance, and trade through an ASIC broker with reliable order execution from the best forex brokers in Australia ranking.
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Diagram is illustrative. Last reviewed: 2026-06-01.
Frequently asked questions
What is a stop loss in trading?
A stop loss is an order that automatically closes a trade at a predetermined price to limit your loss if the market moves against you. You set it when you open the position. For a buy (long) trade, the stop sits below your entry; for a sell (short) trade, above it. If price reaches the stop level, the order triggers and closes the trade at the next available price, capping the loss at roughly the amount you decided in advance. It is the foundation of controlling risk on every trade.
How do you set a stop loss?
Place the stop at a price where your reason for the trade would be proven wrong, not at an arbitrary dollar amount. For a long, that is usually just below a support level or a recent swing low; for a short, just above resistance or a swing high. Once the stop level is set by the chart, you adjust your position size so that the distance to the stop equals only the small percentage of your account you are willing to risk. The chart decides where the stop goes; the position size decides how much that costs.
What is the difference between a stop loss and a take profit?
Both are orders that close a trade automatically at a set price, but in opposite directions. A stop loss closes the trade at a loss to cap the downside if price moves against you. A take profit closes it at a gain to lock in profit when price reaches your target. Used together, they define the full risk and reward of a trade before you enter, which lets you calculate the reward-to-risk ratio and remove emotional decision-making from the exit.
What is a trailing stop loss?
A trailing stop is a stop loss that moves with the price in your favour but never against you. For a long trade, as price rises, the trailing stop follows it up at a set distance; if price then falls by that distance, the stop triggers. It lets you lock in profit as a trade runs while still giving it room to move, and it removes the temptation to exit a winner too early. The trade-off is that a normal pullback can stop you out before a larger move continues.
Where should I place my stop loss?
Place it at a level that invalidates your trade idea, with a small buffer for noise. For a long, that means just below the support, swing low, or moving average you are trading from; for a short, just above the equivalent resistance. Avoid placing the stop too tight, right at an obvious level where normal volatility will hit it, or too wide, where the loss becomes large. The goal is a stop close enough to keep the loss small but far enough to survive ordinary price noise.
Do I really need a stop loss on every trade?
For almost all retail traders, yes. A stop loss is what guarantees a single bad trade cannot become a catastrophic one, and trading without it relies on you closing losers manually under stress, which is exactly when discipline fails. The rare exceptions are advanced strategies with predefined risk built in another way, but for a developing trader, a stop loss on every trade is non-negotiable. The large losses that end accounts almost always come from trades that had no stop.
