Methodology
Forex Position Size Calculator Methodology
How position size in lots (or units) is derived from account size, risk percentage, and stop-loss distance.
By Yadav PatleLast updated:
Formula
Position Size (lots) = (Account × Risk%) ÷ (Stop-Loss pips × Pip Value per lot)
Variables
| Symbol | Name | Description |
|---|---|---|
| Account | Account balance | Current equity in the account currency. |
| Risk% | Risk per trade | The fraction of the account you accept losing on this trade, typically 0.5% to 2%. |
| Stop-Loss pips | Stop distance | Distance from entry to stop, in pips (or points, for non-forex instruments). |
| Pip Value per lot | Pip value | Dollar (or account-currency) value of a 1-pip move per standard lot. ~$10 for most USD-quoted majors, ~$9 for JPY pairs (varies with the cross rate). |
Worked example
$10,000 account, 1% risk, EUR/USD with 50-pip stop: dollar risk = $100, per-lot loss at 50 pips = $500, position size = $100 / $500 = 0.2 lots (20,000 units / 2 mini lots).
Assumptions and limitations
Every model leaves something out. Here is what this calculator assumes, and what it does not model, so you can interpret the output honestly:
- Pip values are pre-mapped per pair using approximate live cross rates. They drift with FX moves; for very large positions, recheck against your broker's instrument specs.
- Spread and slippage are not modelled. Pad your nominal stop by typical spread and worst-case slippage to keep dollar risk on target.
- The calculator sizes one trade in isolation. Correlated positions (long EUR/USD + short USD/CHF, etc.) compound risk, so apply a portfolio-level cap separately.
Authoritative sources
Where the formula, rates, or framework come from:
Try it now
Plug in your own numbers in the Forex Position Size and see the formula applied in real time.
This methodology page is for educational purposes only. Calculations are estimates; real-world results vary with taxes, fees, expense ratios, and market conditions. Yadav Patle is not a SEBI-registered investment adviser. For personalised advice, consult a registered adviser.