Here's a truth that surprises every beginner: professional traders think about how much they can lose long before they think about how much they can make. The reason is simple math — you can't make money if you've blown up your account. This lesson teaches the one skill that separates traders who last from those who don't: risking a small, fixed amount per trade and sizing every position from your stop. It's the least exciting lesson in the course and the most important.

Everything you learned about leverage in Lesson 9 makes this non-negotiable. Power without control is just a faster way to zero.

Risk a small, fixed slice — every time

The core rule: decide in advance the most you'll lose on any single trade, as a small percentage of your account, and never exceed it. Many traders use something like 0.5% to 1% per trade. On a $5,000 account, 1% is $50 — that's the most you'll lose if the trade goes wrong.

Why so small? Because losses come in streaks, and a small risk survives them. Lose 1% ten times in a row and you're down about 10% — annoying, recoverable. Risk 10% per trade and the same streak nearly wipes you out. The law of large numbers guarantees losing streaks will happen; small sizing guarantees they won't kill you.

🚨 DANGER
The fastest way to blow up isn't bad analysis — it's oversizing. One trade risking half your account, one bad gap, and you're done, no matter how good your idea was. Cap the risk per trade and no single loss can end you. This is the heart of the [survival mindset](/learning/trading-survival-mindset/).

Size the position from your stop

Here's the move that ties it together. You don't pick a position size and hope — you work backwards from your risk. Three steps:

  1. Decide your risk in dollars — e.g. 1% of a $5,000 account = $50.
  2. Decide your stop — the price where you'll admit you're wrong and exit. Say that's $2 below your entry.
  3. Divide — $50 risk ÷ $2 per share = 25 shares. That's your size.

Do it in that order, every time. If the stop is far away, you buy fewer shares; if it's close, you can buy more — but the dollars at risk stay the same. Try it:

Position Size Calculator

And to check whether a trade is even worth taking — is the potential reward bigger than the risk? — use a reward-to-risk check:

Risk / Reward Calculator

Why this matters most for leverage and options

Position sizing is what makes leverage safe to touch. A leveraged instrument amplifies the move; correct sizing controls the dollars, so you get the upside of leverage without the account-ending downside. When you reach options in the next lesson, this is the discipline that turns their defined risk into a real edge: you already know your max loss (the premium), so sizing is as simple as "never buy more premium than my risk budget allows." Survive first — the profits are only available to traders who are still in the game. This is the same rigor behind Kelly position sizing and drawdown limits.

Related reading

Next: Lesson 11 — Options, the versatile power tool this whole map leads to.