Portfolio construction
Risk-based position sizing (ATR)
Each position is sized so that a stop placed a few daily ranges away would cost the same share of the account.
The idea in plain words
The trader's way of building a portfolio: decide how much you are willing to lose on each position (e.g. 1% of the account) and where your stop would be (e.g. two average true ranges away). The position size follows. Volatile tickers get small positions, calm ones large positions, and every position risks the same amount.
How it is calculated
ATR(14): the average of the last 14 daily true ranges. Stop distance = ATR multiple × ATR. Units = equity × risk% ÷ stop distance. Weight = units × price ÷ equity. The total is capped at the maximum leverage. Defaults: $10,000 equity, 1% risk, 2 × ATR.
TR = max(high − low, |high − close₋₁|, |low − close₋₁|)
ATR = mean(TR, 14 days)
units = equity × risk% ÷ (k × ATR)
weight = units × price ÷ equityHow to use it
- When you trade with stops and want each position to risk the same.
- Set Settings › equity, risk per position and ATR multiple to your own rules.
- Re-run it when volatility changes; the sizes follow the ATR.
Drawing conclusions
- A sum of weights above 1 means the stops, not the cash, are the binding risk: that is leverage.
- Each position's dollar risk is in the study's notes.
Example
A $10,000 account risking 1% ($100) per position with a 2 × ATR stop. Gold at $2,400 with an ATR of $30: stop $60 away, so 100 ÷ 60 = 1.67 ounces, about $4,000 or 40% of the account. EURUSD at 1.10 with an ATR of 0.0070: stop 0.0140 away, 100 ÷ 0.014 = 7,143 units, about $7,900. Both lose $100 at their stop. In the running example the four positions add up to 132% of the account.
The example's inputs are illustrative; the weights and figures are what our optimiser returns for them.
Watch out for
- Equal stop risk is not equal portfolio risk: correlations are ignored, so four correlated positions risk far more than four times 1% together.
- Gaps through the stop can lose more than planned.
A little history
J. Welles Wilder introduced the ATR in New Concepts in Technical Trading Systems (1978). Richard Dennis and William Eckhardt's Turtle traders (1983) sized every position by "N", the ATR, the best-known use of the method.
Educational content only. No portfolio model knows the future: every one of them works on estimates from the past, and nothing here is investment advice.