Risk Management and Position Sizing

Ask a struggling trader about their strategy and you will hear about entries. Ask about position sizing and you often get a blank look. That is backwards. You can be right about direction and still go broke if the size is wrong. Sizing is the part of trading you actually control.

Risk a fixed fraction, not a fixed amount

The core rule is simple: decide in advance the small percentage of the account you are willing to lose if a trade is wrong, and size every position to that number. A common starting point is one percent per trade. The exact figure matters less than the discipline of using the same one every time.

At one percent, ten losers in a row costs you under ten percent of the account. Survivable. At ten percent per trade, the same streak is close to ruin. Streaks happen to everyone, so the question is only whether they end your account or barely register.

The formula

Three inputs decide the size of any trade:

• Account risk: the cash you will lose if stopped, for example one percent of the account.
• Entry and stop: the price you get in and the price that proves the idea wrong.
• Risk per unit: the distance between entry and stop.

Position size = account risk in cash ÷ risk per unit

Worked example. The account is 10,000 and you risk one percent, so 100 of risk. You enter a stock at 50 with a stop at 48, which is 2 of risk per share. Position size is 100 ÷ 2, which is 50 shares. If the stop hits, you lose 100, exactly as planned. The wider the stop, the smaller the position. The tighter the stop, the larger it can be. The dollar risk never changes.

Why the stop comes first

Notice the order. You do not decide how many shares you want and then find a stop. You decide where the idea is wrong, and the size falls out of the maths. This is the habit that separates traders who last from traders who do not. The stop defines the trade. The size simply serves it.

This is why a clear invalidation matters so much in a setup. A breakout with a defined level gives you a natural stop, which gives you a clean size.

Adjusting for volatility

A quiet large-cap stock and a fast-moving crypto coin do not deserve the same stop distance. Volatile instruments need wider stops to avoid being shaken out by noise, which means smaller positions for the same risk. Sizing by risk rather than by a fixed share count handles this automatically. The wilder the asset, the smaller the position, with no extra thinking required.

The common mistakes

• Sizing by conviction. Feeling sure about a trade is not a reason to risk more on it.
• Moving the stop to fit the size you wanted, rather than sizing to the stop.
• Adding to a loser to lower the average, which quietly multiplies the risk.
• Ignoring correlation. Five trades in the same theme is one big position wearing five hats.

Good sizing is boring, and that is the point. It turns trading from a sequence of life-or-death bets into a process you can repeat for years. Protect the downside, and the upside has time to work.