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Your Stop-Loss Is a Sizing Decision
Most traders think of a stop-loss as an exit. I think of it as a sizing decision you make before you ever enter.
Here is why. Your stop tells you how much the trade can lose per share. Your position size tells you how many shares you own. Multiply the two and you get the only number that actually matters: how much of your account is on the line if you are wrong. Change either one and you change your risk. Most people only think about one of them.
The stop you pick decides the size you can afford
Say you have a 100,000 dollar account and you are willing to lose 1 percent on any single idea. That is 1,000 dollars.
If the stock is at 50 and your stop is at 48, you are risking 2 dollars a share. You can own 500 shares. If your stop is at 45, you are risking 5 dollars a share. Now you can only own 200 shares.
Same account. Same idea. Same 1,000 dollars at risk. Very different positions. The stop did not just decide where you get out. It decided how big you were allowed to be.
That is the part people flip around. They decide on the size first, usually because a round number feels right, and then they put the stop wherever the loss stops hurting. That is backwards. The stop should come from the chart and the trade. The size should come from the stop.
Tight stops are not automatically safer
There is a common belief that a tight stop is the disciplined, low-risk choice. Sometimes it is. Often it is just a way to get stopped out by normal noise and then watch the trade work without you.
Every stock has a normal daily wiggle. I like to look at the average true range to get a feel for how much room a name usually needs. If a stock moves 3 dollars on an ordinary day and your stop is 1 dollar away, you have not set a stop. You have set a coin flip.
The fix is not to stop using stops. The fix is to give the trade the room it actually needs, and then cut the size down so the total dollars at risk stay the same. Wider stop, smaller size. The risk to your account does not change. Your odds of getting shaken out on a random Tuesday do.
Moving the stop is resizing the trade
Here is the behavior that blows people up. The stock drops toward the stop. They do not want to take the loss, so they move the stop lower. Just a little. Just this once.
What they actually did was increase the size of their bet. They own the same number of shares with more distance to the exit, which means more dollars at risk than they planned. They did not hold their discipline. They doubled down without buying a single new share.
If you would never add to a losing trade on impulse, you should not move your stop on impulse either. It is the same decision wearing a different outfit.
Some positions should not have a hard stop at all
I will be honest. On some long-term holdings I do not run a hard stop. If I own a great business as a long-term position and it drops 15 percent on a bad week, I am not dumping it at the low because a line on the chart said so. I would rather set alerts and decide with a clear head.
But that only works because the position was sized for it. If I am not going to use a stop, the size has to be small enough that a big drawdown is uncomfortable, not catastrophic. No stop means the size is your stop. That is the same rule from a different direction.
With options it gets even more direct. When you buy a call or put, the premium you pay is your maximum loss. You do not need a stop to define it. You need to size the premium so that losing all of it is fine. If losing the whole premium would wreck your month, the trade was too big before it started.
A simple routine
Before I put on a trade, I answer three questions in this order.
Where would this trade be clearly wrong? That is the stop.
How many dollars am I willing to lose if it gets there?
Divide the dollars by the distance. That is the size.
Then I do not touch the stop unless the trade has moved in my favor and I am tightening it to lock something in. Tightening protects gains. Loosening adds risk. Only one of those is allowed on impulse, and it is not the second one.
One more thing. A stop is a plan, not a guarantee. Stocks gap through stops on earnings and bad headlines, and you get filled wherever the market opens. That is another reason to keep the size sensible. The gap is the risk your stop cannot see.
The takeaway
A stop-loss is not a safety net you hang after the fact. It is one half of your risk equation, and size is the other half. Pick the stop from the trade, pick the size from the stop, and never let a bad afternoon talk you into moving it.
What to put on your sticky note
Risk is stop distance times size.
Pick the stop first. Let it set the size.
Wider stop, smaller size. Same risk, fewer shakeouts.
Moving a stop lower is adding to a loser.
No stop means the size is the stop.
Education only. Not trade advice. Options involve significant risk and are not suitable for all investors.
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