Stop-Loss Basics: Deciding Where to Be Wrong

A stop-loss is a price you decide in advance: if the trade reaches it, you exit and accept the loss. It sounds simple, but how you handle stops separates traders who survive from those who don’t.

Why a stop-loss matters

Every trade can go wrong. A stop-loss does two things:

1. Caps your loss so one bad trade can’t do serious damage.
2. Defines your risk so you can size the position correctly before you enter.

Without a predefined stop, a small loss can quietly grow into a large one while you “wait for it to come back.” That hope is how accounts get destroyed.

Where traders place stops

There’s no single correct spot, but common approaches include:

• Below support (or above resistance) — place the stop just beyond a level that, if broken, means your idea was wrong.
• Beyond a recent swing low/high — using the chart’s own structure as the line in the sand.
• A fixed percentage or amount — simple, though it ignores where the chart’s natural levels are.

The best stop is at a price where, if hit, your reason for the trade is genuinely invalidated — not just a random distance away.

The link to position sizing

This is the crucial connection. Your stop distance is what lets you size a position correctly:

Shares = (Account × Risk%) ÷ Stop distance per share

A stop placed at a sensible level gives you a stop distance, and that distance tells you exactly how many shares keep your risk fixed. Stop placement and position sizing are two halves of one decision.

Mistakes that quietly hurt

• Moving the stop further away when price approaches it — this turns a planned small loss into an unplanned big one.
• No stop at all — relying on willpower to exit in the moment, which rarely works under stress.
• Stops too tight — placed so close that normal noise stops you out before the idea has a chance.

A realistic expectation

A stop-loss won’t make you profitable on its own, and stops do get hit by random noise sometimes. Its job is survival — keeping any single loss small enough that you live to trade again. This is educational material, not financial advice.

Try the calculator

Once you’ve chosen a stop level, the Position Size Calculator turns that stop distance into the exact share count that keeps your risk where you want it. Decide your stop first, then size around it.