Position size = (account value × risk per trade %) ÷ (entry price − stop price). Decide the stop from the chart first, then let the formula determine the share count. Most swing traders use 0.5%–2% risk per trade, chosen so that a realistic losing streak stays inside a drawdown they can sit through.
A $50,000 account, risking 1%, entering at $71.65 with a stop at $68.00:
Note what the formula does not consider: how much you like the setup. Conviction belongs in whether you take the trade, not in how large it is. Sizing by conviction is how a single trade becomes 40% of an account.
The stop comes first, from the chart — below the base, below the 21 EMA, below the low of the entry day. Whatever your method, it is a price the chart gives you, not a percentage you pick.
Then the formula returns a share count. If that share count feels too small, the correct response is to accept it, not to widen the stop.
Where the stop goes also decides how large the position can be, which is a bigger lever than most traders realise. Working the other way round — deciding you want 500 shares and placing the stop wherever that makes the risk acceptable — puts your stop at an arbitrary price with no relationship to the chart. That is the single most common sizing mistake, and it disguises itself as conviction.
1% is the common default and a reasonable starting point. But it is worth deriving rather than assuming, because the right number depends on your win rate.
A 40% win rate produces losing streaks of five or six regularly. Not as a disaster — as ordinary variance. So the question is not "what feels safe?" but "what does a normal bad run cost me at this size?"
| Risk per trade | 5 losses in a row | 8 losses in a row |
|---|---|---|
| 0.5% | −2.5% | −4.0% |
| 1.0% | −5.0% | −8.0% |
| 2.0% | −10.0% | −16.0% |
| 3.0% | −15.0% | −24.0% |
Pick the row whose numbers you could sit through without abandoning the strategy. That is your risk percentage. It is a psychological constraint priced in arithmetic, and it is a far better basis than a round number.
Risk per trade controls what a loss costs. It does not control concentration.
In the example above, 1% risk produced a position worth 19.5% of the account, because the stop was tight. Five such positions and you are 97% invested — each individually well-risked, collectively exposed to one bad overnight gap across a correlated sector.
So cap both: a maximum risk per trade and a maximum position size as a percentage of the account, whichever binds first. A tight stop should not be allowed to justify an enormous position.
A stop is not a guarantee. A stock that closes at $69 and opens at $58 on an earnings miss fills far below your stop, and your 1% risk becomes 4%.
This is not an argument against stops — it is an argument for knowing when the risk is unbounded. Holding through earnings is the clearest case, which is why knowing the next earnings date before sizing a swing position matters more than almost any other input.
Risking more when things are working and less when they are not is defensible if it is systematic — progressive exposure is the structured version of it. Tie it to a measurable input — a rolling win rate over the last twenty trades, say — with defined tiers, and write the tiers down before you need them.
What does not work is discretionary scaling in the moment, because the moment you feel most confident is usually after a winning streak, which is statistically the worst time to add risk.
Position sizing is risk management, not investment advice. The arithmetic here is general; the right risk level for you depends on circumstances no article can know.
TradePiko's Position Sizing Advisor calculates your risk per trade from your rolling win rate, sized so a realistic losing streak stays inside a 5% monthly drawdown — and shows on every past trade what it would have recommended at the time.
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