Understand How a Trailing Stop-Loss Works

How a trailing stop loss works

A normal stop loss sits at a fixed price. A trailing stop moves:

• For a long position, the stop rises as the price rises, by a fixed amount, a percentage or an indicator value. It never falls.
• For a short position, the stop falls as the price falls. It never rises.

When the price reverses by the trailing distance, the stop is hit and the position exits.

Three ways to trail

Fixed distance

The stop sits a fixed number of points or a fixed percentage below the highest price reached. It is easy to understand and to automate. The weakness is that the same distance is too tight on a volatile day and too loose on a quiet one.

ATR-based

The average true range measures how much the instrument moves in a typical candle. A stop at 2 to 3 times the ATR adapts to the market: wider when volatility rises, tighter when it falls. If Nifty's 14-period ATR on a 15-minute chart is 40 points, a 2.5 ATR stop trails 100 points behind the high. Our ATR volatility strategy guide shows the indicator in use.

Indicator-based

The stop follows a line on the chart. A trade exits when the price closes below a 20-period moving average, or below the Supertrend line, or below the lowest low of the last three candles. These stops follow the trend's shape rather than a fixed distance. See the Supertrend strategy for an example.

Setting the distance

The distance decides the trade-off between giving back gains and being stopped out by noise.

• Too tight: normal fluctuations hit the stop, and the strategy exits good trades early with small gains.
• Too loose: large gains are given back before the stop triggers.

Guidelines that work in practice:

1. Measure the instrument's normal movement on your timeframe, using ATR or the average range of recent candles.
2. Start with a distance of 2 to 3 times that measure.
3. Test distances on either side in a backtest and compare the average profit per trade, not only the win rate.
4. Keep the distance fixed for the life of the trade, or widen it only by a rule you tested.

A trailing stop that tightens as the gain grows, for example from 3 ATR to 1.5 ATR once the trade is up 2 ATR, protects more of a large gain at the cost of more early exits.

Trailing stops on options

Option prices move faster than the index and lose value with time, so the same rules need care:

• Trail the index, not the premium. An option's price can fall 20% while the index is unchanged, because of time decay or lower IV. Many traders set the trail on the underlying's level and exit the option when it triggers.
• Trail the premium for bought options. For a long call or put, a stop at 30% to 50% below the highest premium is common, with a wide distance because option prices are noisy.
• For sold options, trail the profit. A short straddle that has earned 60% of its premium can carry a stop that exits if the profit falls back to 40%. QuantPower's MTM stop loss can trail the combined profit of all legs.

Trailing stops and exchange orders

Indian exchanges do not offer a trailing stop order type. A trailing stop is a rule that your platform or your own code runs: it watches the price and modifies a stop-loss order, or sends an exit order, when the rule says so. Three things follow:

• The trail works only while the platform is connected and your broker session is active.
• Each modification is an order, so a trail that updates on every tick can exceed order limits. Updating once a candle, or only when the stop moves by at least a tick size, keeps the count low.
• The exit order is a limit or stop-loss order with the usual fill risk. Our guide to order types explains the choices.

Where trailing stops fail

• Gaps. A trailing stop cannot exit at a price the market skips. An overnight gap through the stop fills at the open, wherever that is.
• Whipsaws. In a sideways market, a tight trail exits repeatedly for small losses.
• Illiquid contracts. A stop that triggers in a thin option may fill far from the trigger. Use limit orders with a buffer.
• Early exits in strong trends. A trend with sharp pullbacks stops out a tight trail before the main move.

No stop removes risk; it limits how much of a move you give back once the trade has gone your way.

Trailing stops in an automated strategy

Automation suits trailing stops well, because the rule needs constant attention and no judgement. In QuantPower's strategy builder:

1. Set the initial stop loss for the position, in points, percentage or premium.
2. Switch on trailing and choose the step: for example, move the stop up by 50 points for every 50 points the index gains.
3. For sold option strategies, set a profit-based trail on the combined MTM instead.
4. Backtest the strategy with and without the trail to see whether it improves the average profit per trade.

The MTM stop loss works across all open positions and can trail the account's total profit, which protects a day's gains after the individual strategies have done their work.

Backtesting a trailing stop

Compare the strategy with a fixed stop and target against the same strategy with a trailing stop, on the same data. Look at:

• the average profit per trade,
• the largest single gain, which trails often reduce,
• the maximum drawdown, and
• the number of trades, which tight trails increase.

A trail helps most in trending markets and hurts most in ranges. Test across both. Our guide on how to backtest trading strategies covers the method.

Frequently asked questions