What Is a Stop Loss?

A stop-loss is an instruction to your broker to close a position if the price reaches a specified level that is worse than your entry. Its purpose is to cap the loss on a single trade at an amount you decided in advance, rather than one the market decides for you. It is the most basic risk-management tool available to a trader, and it underpins position sizing, risk-to-reward planning and long-term survival.

How a stop-loss works

When you open a trade you can attach a stop-loss at a specific price. The order sits with the broker and does nothing until the market reaches it. At that point it is triggered and the position is closed at the best available price.

• On a long position the stop is placed below the entry price and is triggered when the bid falls to that level.
• On a short position the stop is placed above the entry price and is triggered when the ask rises to that level.

The distinction between bid and ask matters. Charts usually show the bid or the mid-price, so a long trade's stop can be hit by the bid while a short trade's stop responds to the ask, which sits one spread higher. When spreads widen around news, a stop can trigger even though the price on the chart appears not to have reached it.

A worked example

You buy 0.5 lots of EUR/USD at 1.0850 and set a stop-loss at 1.0820.

• Stop distance: 1.0850 − 1.0820 = 0.0030 = 30 pips
• Pip value for 50,000 units: $5
• Maximum planned loss: 30 × $5 = $150

If the bid falls to 1.0820, the position is closed and the loss is approximately $150 plus any slippage. If the price rises instead, the stop simply never triggers. The position size calculator reverses this calculation, giving you the lot size that matches a chosen risk amount and stop distance.

Why a stop-loss is essential

It defines risk before the trade, not after

Once you are in a losing trade, decisions become harder. A pre-set stop removes the temptation to "give it a little more room" repeatedly until a small loss becomes a large one. Trading Psychology explores why that temptation is so strong.

It makes position sizing possible

You cannot size a position sensibly without knowing where it will be closed if wrong. The stop distance is the input that converts a risk amount in money into a lot size.

It protects against the unexpected

Markets can move sharply on unscheduled news, and a trader cannot watch every position at every hour of a 24-hour market. A resting stop provides coverage when you are away from the screen.

It keeps losses survivable

Losing trades are unavoidable. The goal of risk management is to keep each loss small enough that a run of them does not end your trading. A trader risking 1% per trade can lose ten times in a row and still have around 90% of the account. Without stops, one trade can do far more damage than that.

Types of stop-loss orders

A trailing stop is worth understanding in a little more detail. If you buy at 1.0850 with a 30-pip trailing stop, the initial stop is at 1.0820. If the price rises to 1.0900, the stop follows to 1.0870. If the price then falls, the stop stays at 1.0870 and the trade closes there, banking a 20-pip gain. Trailing stops are attractive but can be triggered by normal pullbacks if set too tight.

Where to place a stop-loss

The stop should be at a level where, if reached, your reason for the trade is no longer valid. There are several common methods.

Structure-based stops

Place the stop just beyond a support or resistance level, a recent swing high or low, or a pattern boundary. If the price breaks through that level, the setup has failed. This is the most widely used approach in discretionary trading and is covered in Support and Resistance Explained.

Volatility-based stops

Use a measure of recent volatility, such as the Average True Range (ATR), to set the distance. A stop at 1.5 × ATR adapts automatically: wider in volatile conditions, tighter in quiet ones, which reduces the chance of being stopped out by noise.

Percentage or fixed-pip stops

Some traders always use a fixed distance, such as 20 pips or 1% of price. This is simple but ignores market conditions; a fixed 20 pips may be far too tight for GBP/JPY and too wide for EUR/CHF.

Time-based stops

Close the trade if it has not moved in your favour within a set period. This is usually used alongside a price stop, not instead of one.

Whichever method you use, decide the stop first and the position size second. A stop placed to suit a position size that is already too large is not risk management.

Limitations of stop-loss orders

Slippage

A standard stop becomes a market order when triggered. In normal conditions it fills close to the stop price; in fast markets or across a weekend gap it can fill some distance beyond it. The loss is then larger than planned. What Is Slippage? explains the causes and how to reduce exposure to it.

Stop hunting and noise

Placing stops at obvious round numbers or just below widely watched levels makes them vulnerable to brief spikes. Giving the stop a little extra room beyond the level, and sizing the position accordingly, can help.

Widening spreads

As noted, stops are triggered by the bid or ask, not the mid-price. During the seconds around a major release, spreads may widen enough to trigger stops that would otherwise have been safe. The economic calendar shows when such releases are scheduled.

Common mistakes

1. Moving the stop further away once the trade is losing. This converts a defined risk into an undefined one.
2. Setting stops too tight to keep lot size large, which leads to repeated small losses on trades that would have worked.
3. Using the same pip distance on every pair regardless of volatility.
4. Trading without a stop on the basis that you will watch the position, which fails the first time you are away from the screen during a sharp move.
5. Relying on the broker's stop-out as the exit; it fires at a level determined by your margin, not by your analysis.

For step-by-step guidance on placing the order on the platform, see How to Set Stop Loss and Take Profit.

Key takeaways

• A stop-loss automatically closes a trade at a predefined worse price, capping the loss on that position.
• Long stops are triggered by the bid, short stops by the ask, so spread widening can trigger a stop the chart does not appear to reach.
• The stop distance in pips multiplied by pip value gives the planned risk, and it is the basis of position sizing.
• Structure, volatility and fixed-distance methods each have trade-offs; the stop should sit where the trade idea is invalid.
• Standard stops can slip in fast markets; guaranteed stops, where offered, remove that risk for a premium.
• Decide the stop before the trade, and never move it further from entry once the position is open.