Position Size Calculator
Enter your account balance, how much you want to risk and where your stop-loss is. You get the position size that keeps a losing trade at the amount you chose.
Contract size is pre-filled with the usual value. Check your broker’s spec sheet, as some brokers differ.
Fill in your balance, entry and stop-loss to see your position size.
The position size formula
Position size = (balance × risk %) ÷ loss per lot at your stop. The loss per lot depends on how far your stop is from your entry and how much one unit of price movement is worth for that instrument.
Worked example: EURUSD
- Account: $10,000. Risk: 1%, so the amount at risk is $100.
- Entry 1.0850, stop-loss 1.0820, which is a 30-pip stop (0.0030).
- Loss per standard lot at that stop: 0.0030 × 100,000 = $300.
- Position size: $100 ÷ $300 = 0.33 lots (rounded down).
Once you have taken the trade, track whether you stuck to your sizing. Your profit factor shows whether your results are paying off, and a trading journal shows which pairs and sessions cost you the most.
Position sizing questions
How do I calculate position size?
Work out how much money you are willing to lose (account balance × risk %), then divide it by how much you lose per lot or unit if your stop-loss is hit. The result is the largest position that keeps your loss at your chosen amount.
What percentage of my account should I risk per trade?
There is no single right answer. Many traders risk between 0.5% and 2% per trade so that a losing streak doesn’t do serious damage. Prop firms often set their own daily and total loss limits, so check those rules too.
How do I calculate lot size in forex?
Lot size = amount at risk ÷ (stop distance in price × contract size). For a USD-quote pair like EURUSD, a standard lot is 100,000 units, so each pip (0.0001) is worth about $10 per lot. This calculator does that for you and rounds down to the nearest 0.01 lot.
Why is the lot size rounded down?
Brokers accept lot sizes in steps, usually 0.01. Rounding down means your real loss can be slightly under your target but never above it.
Does this work for crypto and stocks?
Yes. Choose the per-unit option. Position size is your risk amount divided by the distance between entry and stop-loss, so it works for coins, shares and any asset priced per unit. It does not account for leverage, margin or fees.
Does this calculator save my numbers?
No. Everything is calculated in your browser, and nothing you enter is uploaded or stored.
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