What a stop loss does
A stop condition defines when a trader intends to exit because the trade has moved adversely or the original setup is considered invalid.
Stop order mechanics
A stop-market style order generally triggers an order intended for immediate execution. A stop-limit order triggers a limit order and therefore introduces the possibility of not filling.
Why actual loss can exceed planned loss
Fast markets, gaps, thin liquidity and large orders can cause execution away from the trigger price.
Stop placement and position size belong together
A wider stop generally requires a smaller position if the trader wants to keep the same monetary risk. A tighter stop generally permits more exposure mathematically, but may be more vulnerable to normal market noise.
Common mistakes
Assuming stop price equals fill price
A triggered market-style stop can execute at worse prices when liquidity is insufficient.
Moving a stop simply to avoid taking a loss
Changing the exit without reassessing position risk can increase the loss beyond the original plan.
Placing stops without market context
A stop should relate to both risk tolerance and the logic that invalidates the setup.
Trigger price and execution price are different concepts
A stop trigger determines when an exit instruction becomes active. The resulting order must then execute in the available market.
During fast movement or thin liquidity, the eventual fill can occur beyond the trigger level. This is one reason a stop defines an exit mechanism rather than guaranteeing an exact loss.
Know which price activates the stop
Derivatives venues may allow conditional orders to reference last price, mark price or index price. These prices can temporarily differ during volatile trading.
A strategy should document the selected trigger reference so live execution and historical testing use comparable rules.
Price structure and volatility can inform stop design
Some strategies place stops beyond a defined structural invalidation point; others use volatility measures such as ATR to scale distance. Both approaches still require a position size compatible with the resulting stop distance.
Moving a stop farther away after entry without reducing exposure increases the amount at risk.
No stop mechanism can guarantee a specific fill price in every market condition.
Key takeaways
- A stop loss defines an intended adverse exit condition.
- Trigger price and final execution price can differ.
- Stop distance and position size should be considered together.
- Stops reduce risk but cannot eliminate execution risk.
Sources & further reading
This lesson is educational material. Market structure, exchange rules, fees, margin requirements and derivatives mechanics can differ by venue and can change over time. Verify current rules with the venue you use.