What is the Lot Size Calculator?
A lot size calculator tells you exactly how many lots to trade so a losing trade costs only a fixed, pre-decided amount of your account. In forex, position size is measured in lots — a standard lot is 100,000 units, a mini lot 10,000, and a micro lot 1,000 — and getting that number right is the core of survivable risk management.
Instead of guessing, you anchor every trade to three things you already know: how much you'll risk, how far away your stop-loss sits in pips, and the value of one pip. The calculator turns those into the precise lot size that keeps your risk constant trade after trade.
How to use it
- 01Enter your account balance — the capital you actually trade with.
- 02Choose the percentage of the account you're willing to risk on this trade (most professionals use 1–2%).
- 03Enter your stop-loss distance in pips — the gap between your entry and your stop.
- 04Enter the pip value per standard lot for your pair (about $10 for most USD-quoted pairs). The calculator returns the exact lot size.
The formula
Multiply the result by 100,000 for units, or by 10 / 100 to express it in mini / micro lots.
Worked example
You have a $10,000 account and risk 1% ($100) on a EUR/USD trade with a 25-pip stop. Pip value is $10 per standard lot.
Lots = $100 ÷ (25 × $10) = $100 ÷ $250 = 0.40 standard lots.
That's 40,000 units (4 mini lots). If price hits your stop 25 pips away, you lose exactly $100 — your planned 1%.
Frequently asked questions
What is a lot in forex?+
A lot is the standard unit of trade size. One standard lot is 100,000 units of the base currency, a mini lot is 10,000 units (0.1 lots), and a micro lot is 1,000 units (0.01 lots). Lot size determines how much each pip move is worth.
How do I calculate the correct lot size?+
Divide the cash you're willing to risk (account × risk%) by your stop-loss distance in pips multiplied by the pip value per lot. The result is the lot size that caps your loss at exactly your chosen risk.
What pip value should I enter?+
For pairs quoted in USD (like EUR/USD or GBP/USD), one pip is worth about $10 per standard lot. For other pairs it varies with the exchange rate — use our pip calculator to find the exact figure, then bring it back here.
Why does lot size matter so much?+
Trading too large is the fastest way to blow up an account. By sizing every position to a fixed percentage risk, a string of losses does only limited, predictable damage — letting you stay in the game long enough for your edge to play out.
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For educational purposes only. Not financial advice.