Position Size Calculator Guide: The Formula for Forex, Stocks, Crypto and Futures (With Worked Examples)

The complete position sizing guide: one formula that works for every market, worked examples for stocks, forex, crypto and futures, how to size from an ATR stop, and why risk per trade matters more than leverage.

In this guide

1. 1. Why Position Size Decides Whether You Survive
2. 2. The Position Sizing Formula
3. 3. Worked Example: Stocks
4. 4. Worked Example: Forex Lot Size
5. 5. Worked Example: Crypto
6. 6. Worked Example: Futures
7. 7. Sizing From an ATR-Based Stop
8. 8. Fees, Slippage and Gaps
9. 9. How Much Should You Risk Per Trade?
10. 10. Portfolio Heat: Sizing Across Several Positions
11. 11. Position Sizing Mistakes
12. 12. Frequently Asked Questions

FAQ

How do I calculate position size?

Multiply your account equity by your risk percentage to get the dollar risk, then divide by the loss per unit if your stop is hit, which is the distance between entry and stop. The result is the number of shares, coins or base units to trade.

How do I calculate lot size in forex?

Divide your dollar risk by the product of your stop in pips and the pip value per lot. For a 5,000 dollar account risking 1% (50 dollars) with a 25 pip stop on EURUSD, where a standard lot is 10 dollars per pip, the lot size is 50 / (25 x 10) = 0.20 lots.

What percentage of my account should I risk per trade?

Many traders use between 0.5% and 2% of equity per trade, with newer traders often at the lower end. The right number depends on your strategy, your win rate, your drawdown tolerance and any account limits such as prop firm drawdown rules.

Does leverage change my position size?

Not for risk purposes. Your position size comes from your risk amount and stop distance. Leverage only determines how much margin the broker requires, so make sure you have enough margin to hold the size the formula gives you.

Why should I round position size down?

Rounding down guarantees that rounding error can only reduce your risk, never increase it. Rounding up quietly exceeds your planned risk on every trade.