Stop-loss
In short
#TradingA stop-loss is a pre-set price at which a position is closed to cap the loss. It converts an open-ended risk into a defined one that you choose before entering.
Why it matters
Every properly specified trade idea has one, which is why its absence is a useful filter. A call that gives you an entry and a target but no stop has not told you what would prove it wrong. The stop is where the thesis is defined as broken, not merely where you would be uncomfortable.
Example
You buy at $100 with a stop at $92. Your risk is $8 per share regardless of how far the stock ultimately falls, provided the market is liquid enough for the order to fill near your level.
Frequently asked
Does a stop-loss guarantee I lose no more than planned?
No. A standard stop becomes a market order once triggered, so in a gap down or thin market it can fill well below your level. A stop-limit avoids a bad fill but may not execute at all.
Where should a stop go?
Common practice is just beyond a level that would invalidate the reason for the trade, so under a support level or a recent swing low. Placing it at a round loss figure instead ties your exit to your account rather than to the market.