Position sizing
What Is the 2% Rule in Trading?
By MarketsBench · Published · Updated · 4 min read
Step 1 of 6 in Trading Foundations.
The 2% rule says no single trade may lose more than 2% of your account equity. It is a cap on risk, not a cap on position size — and confusing those two is the most common way traders get it wrong.
The rule in one formula
Before entry, you need three numbers: account balance, the percentage you are willing to lose, and the distance from entry to stop.
Risk amount = balance × risk %
Position size = risk amount ÷ per-unit risk
On a $10,000 account, the 2% rule sets the risk amount at $200. If you buy a stock at $50 with a stop at $48, the per-share risk is $2, so you buy $200 ÷ $2 = 100 shares.
Notice what that position is worth: 100 × $50 = $5,000, or half the account. The 2% rule did not tell you to put 2% of the account into the trade. It told you to structure the trade so that being wrong costs $200.
Why the rule exists: surviving a losing streak
Losing streaks are not unusual — they are guaranteed. A strategy that wins 50% of the time will produce a run of six losses roughly once every hundred trades. The rule's real job is making that run survivable.
Because each loss is a percentage of the current balance, the damage compounds downward rather than adding up in a straight line. Ten consecutive losses do not cost 10 × 2% = 20%:
| Risk per trade | After 10 losses | After 20 losses | Gain needed to recover 20 losses |
|---|---|---|---|
| 1% | −9.6% | −18.2% | +22.2% |
| 2% | −18.3% | −33.2% | +49.8% |
| 5% | −40.1% | −64.2% | +179.5% |
The right-hand column is the point. At 1% risk, a brutal 20-trade losing run leaves you needing a 22% gain to get level — a bad quarter. At 5%, the same run requires you to nearly triple what is left. The rule is not about any one trade; it is about making sure a normal cold streak does not end the account.
When 1% is the better number
2% is a ceiling, not a target. Risk less than 2% when:
- You are new, or the strategy is new. Until you have 100+ trades of real data, you do not know your win rate. Size for the possibility that your edge is smaller than you think.
- You hold several correlated positions. Four long tech stocks at 2% each is not four 2% risks; on a sector-wide down day it is closer to one 8% risk. Budget risk per theme, not only per ticker.
- You trade a funded or prop account. A 5% daily loss limit and a 10% maximum drawdown leave no room for 2% swings — most funded traders run 0.25%–0.5%.
- Your account is small enough that fees matter. On a $2,000 account, 2% is $40, and commissions plus spread can eat a meaningful slice of that.
Professional discretionary traders commonly risk 0.5%–1%. The 2% figure is best read as the outer edge of reasonable rather than the default.
Three ways the rule gets misapplied
Risking 2% of the position instead of 2% of the account. A $5,000 position with a 2% stop risks $100 — which may be 1% of your account, or 10% of it. The percentage must always be taken against equity.
Ignoring gaps and slippage. The 2% is what you lose if the stop fills at your price. Overnight gaps, news events and thin markets can fill far worse. Treat 2% as the planned loss, not the worst case, and size down further when holding through earnings or a data release.
Letting the stop drift to fit the size. The order matters: pick the stop from the chart first, then let the formula tell you the size. Traders who decide on the size first end up moving the stop closer to justify it, which guarantees getting shaken out of good trades.
Putting it to work
Before every trade, in this order:
- Mark the stop where the chart says the idea is wrong.
- Multiply your balance by your risk percentage to get the risk amount.
- Divide the risk amount by the entry-to-stop distance to get the size.
- Round down, never up.
Recalculate every time. The stop distance changes with every setup, so a size that was right last week is only right this week by coincidence.