Stop-Loss Order

A stop-loss automatically sells a holding once it falls to a set price, capping further damage.

Why investors care

It is the disciplined exit that removes emotion from cut decisions.

Where people go wrong

In a gap-down it can fill far below the stop; it limits, not eliminates, loss.

In the real market

An investor buys a stock at $50 and sets a stop at $47. The company announces a surprise earnings miss after the close, and the stock opens the next morning at $41 — below the stop. The stop triggers a market order that fills near $40, a 20% loss instead of the planned 6%. The stop did its job mechanically but could not protect against the overnight gap. This is why stop-losses are risk-managers, not guarantees: they work in slow slides and fail in fast gaps.

Using it in practice

Set stops at levels that represent a real thesis break, not a round number. In volatile stocks, a stop too tight gets shaken out by noise; account for the gap risk by sizing positions so the worst-case fill is still survivable.

Example in numbers

Key takeaway

A stop-loss converts an emotional exit decision into a mechanical one, which helps investors who freeze during losses — but it does not guarantee the price. In a fast drop or an overnight gap, the fill can be far below the stop, so it limits damage rather than eliminating it. Set stops where the thesis actually breaks, not at round numbers, and size positions so even a bad fill is survivable. The stop is a risk-manager, not a promise.

Definitions reviewed by the Investing Glossary editorial team.