Position size & stop loss calculator
Enter your account size, how much of it you are willing to lose on this trade, and where your stop is. The calculator returns the quantity to trade, rounded down to your minimum lot.
Result
Fill in the fields to see the result
How it works
Position sizing starts from the loss you accept, not from the amount you want to buy. If your stop is hit, you lose exactly the risk you chose, no more.
A stop below the entry means a long trade; a stop above the entry means a short. R-multiple prices move away from the stop in the profitable direction.
Formula
- Max loss = account size × risk %
- 1R = |entry − stop|
- Quantity = max loss ÷ 1R, rounded down to the minimum lot
- kR price = entry ± k × 1R (+ for long, − for short)
- ATR stop = entry ∓ N × ATR
Example
Account 100,000, risk 1%, buy at 10.00 with a stop at 9.50: max loss is 1,000, 1R is 0.50, so the quantity is 2,000 shares (20 lots of 100). 1R, 2R and 3R are 10.50, 11.00 and 11.50.
FAQ
What risk per trade should I use?
That depends on your strategy and drawdown tolerance. The calculator takes any value you enter and does not recommend one.
Why is my quantity 0?
One minimum lot already risks more than you allow. Move the stop closer, raise the risk, or skip the trade.
Does it include fees and slippage?
No. Real losses can be slightly larger than the max loss shown, especially in fast markets or gaps.
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Calculations only, not investment advice. Check fees, margin rates and contract specs with your broker or exchange.