Position Sizing 101: How Much Should You Risk Per Trade?
*Educational content only. Not financial advice. Trading involves substantial risk of loss.*
New traders spend most of their time looking for entries. Experienced traders spend more time on how much to trade. Position sizing determines whether a losing streak is an annoyance or the end of your account.
The core idea: risk a fixed fraction
With fixed-fractional sizing, you risk the same small percentage of your account on each trade. Many educational sources suggest something in the range of 0.5% to 2% per trade. The exact number is a personal decision, but the principle is the same: no single trade should be able to do serious damage.
The formula
- Account risk ($) = account size × risk percent.
- Per-share risk ($) = entry price − stop-loss price (for a long).
- Position size (shares) = account risk ÷ per-share risk.
Worked example
- Account: $10,000. Risk per trade: 1% → $100.
- Entry: $50.00. Stop: $48.00 → per-share risk $2.00.
- Position size = $100 ÷ $2.00 = 50 shares (a $2,500 position).
If the stop is hit, you lose about $100 (plus slippage and fees). Notice that the position value ($2,500) and the risk ($100) are very different numbers. Sizing is about risk, not position value.
Why it matters: the math of losing streaks
Every strategy has losing streaks. Compare two traders who each hit 10 losses in a row:
| Risk per trade | Approx. account remaining after 10 straight losses |
|---|---|
| 1% | about 90% |
| 2% | about 82% |
| 5% | about 60% |
| 10% | about 35% |
(Calculated as (1 − risk)^10.) Deep drawdowns are also hard to recover from: losing 50% requires a 100% gain just to get back to even.
Adjusting for volatility
Some traders set stops using a volatility measure such as Average True Range (ATR), for example a stop 1.5× ATR from entry. Volatile instruments get wider stops and therefore smaller positions, keeping dollar risk constant.
Options and leveraged products
For defined-risk options trades, the maximum loss is usually the premium paid (or spread width minus credit). Size so that maximum loss equals your account risk. Leveraged products and futures can lose more than expected through gaps, so be conservative.
Put it in your journal
Record planned dollar risk for every trade and compute R-multiples in your trading journal. Over time you will see whether you actually stick to your risk rule.
Checklist before every trade
- Do I know exactly where my stop is?
- Does the position size match my risk rule?
- Could I accept this loss calmly?
- Am I within my daily maximum loss limit?
If any answer is no, do not take the trade. Protecting capital is the first job of every trader.