Lot Size Calculator

Work out the exact lot size for your next trade based on your account balance, the amount you’re willing to risk, and your stop-loss in pips. The calculator converts everything into your account currency for you, so the size it returns is the size you can actually place.

How to use it

1. Account currency. Pick the currency your trading account is denominated in. All results — risk amount, pip value, lot size — will be returned in this currency.
2. Account balance. Enter your current account balance (or the balance you want to size from, if you’re testing a scenario).
3. Risk mode. Choose % of balance if you follow a fixed percentage risk rule (e.g. 1% per trade), or Fixed amount if you cap risk at a specific cash figure (e.g. $200 per trade).
4. Risk percentage or risk amount. Enter the value that matches the mode you picked.
5. Instrument. Search for and select the pair, index or CFD you’re trading. The instrument controls the pip definition and the quote currency used for conversion.
6. Stop-loss (pips). Enter the distance between your entry and your stop, in pips. For JPY pairs, one pip is 0.01; for most other forex pairs it is 0.0001.
7. Hit Calculate lot size. The calculator returns the recommended lot size, the unit equivalent, and the risk amount in your account currency.

A worked example

Suppose you trade a £10,000 GBP account with a 1% risk rule, and you want to take a EUR/USD long with a 25-pip stop.

• Account balance: 10,000 GBP
• Risk: 1% → 100 GBP at risk
• Instrument: EUR/USD
• Stop-loss: 25 pips

The calculator works out the pip value for EUR/USD in GBP (using the live GBP/USD rate), then divides your 100 GBP of risk by the cost of a 25-pip move at one standard lot. The result is the lot size that keeps the worst-case loss at, or just under, your 100 GBP risk cap.

When to use it

• Pre-trade sizing. Every time you place a trade with a planned pip-based stop — before clicking, run the numbers so the size matches your risk rule rather than your gut.
• Backtesting and forward-testing. When you’re evaluating a strategy with a known average stop distance (e.g. “30 pips on the H1”), this tells you what lot size to model so the results reflect realistic risk.
• Scalping vs swing trading. Scalpers running tight 5–10 pip stops can size up while staying within their risk rule; swing traders with 80–150 pip stops need to size down. The calculator handles both without you having to redo the maths.
• Switching instruments. The same 30-pip stop on EUR/USD, USD/JPY and GBP/AUD does not represent the same cash risk. The calculator adjusts for pip value and account-currency conversion automatically.

The formula

Lot size = Risk amount ÷ (Stop-loss in pips × Pip value per lot in account currency)

Common mistakes

• Mixing up pips on JPY pairs. A 50-point move on USD/JPY is 50 pips, not 5,000. The calculator handles this automatically, but it’s worth understanding so you check the output looks right.
• Forgetting to update the account balance. Risk is a percentage of your current balance, not last month’s. Update the input before each session.
• Risking too much, too often. A 1–2% rule per trade is the convention for a reason — sizing up to 5% per trade can blow an account in a single losing streak.
• Ignoring broker lot increments. Brokers usually round to 0.01 lots (micro). The calculator gives you the ideal size; you may have to round down slightly when placing the order.

Related calculators

• Position Size Calculator — same idea, but uses entry and stop-loss prices instead of a pip distance.
• Pip Value Calculator — see what a single pip is worth before deciding on a stop.
• Margin Calculator — once you know the lot size, check how much margin it will lock up.

These calculators are for educational purposes only. Trading leveraged products carries a high level of risk and may not be suitable for all investors.