Forex Lot Size Calculator
Enter your account size, the percentage you will risk, your stop distance in pips and the pip value per standard lot, and this returns the exact lot size — standard, mini and micro — that makes the stop cost precisely your risk budget.
Lot sizes, in units
- Standard lot = 100,000 units. Pip value ≈ $10 on a USD-quoted pair.
- Mini lot = 10,000 units. Pip value ≈ $1.
- Micro lot = 1,000 units. Pip value ≈ $0.10.
The calculator returns all three because most retail platforms accept fractional standard lots, and reading "0.40 lots" as four mini lots is often clearer.
The formula
Lots = (account × risk %) ÷ (stop in pips × pip value per lot). The default gives $100 of risk over a 25-pip stop at $10 a pip, which is 0.40 standard lots.
Notice how sensitive it is to the stop. Halve the stop to 12.5 pips and the position doubles to 0.80 lots. The risk stays at $100 either way — but the leverage on the account has doubled, and so has the damage from a gap through the stop over a weekend or a news release.
Pip value is not always $10
It is $10 per standard lot when the quote currency is your account currency — EUR/USD in a USD account. It is not for JPY pairs (where a pip is 0.01, not 0.0001), for crosses that do not involve your account currency, or for any pair where the quote currency needs converting back. Get the right figure from the pip value calculator before sizing, because an incorrect pip value scales the entire position by the same error.
Leverage does not appear in this calculation
That is deliberate. Leverage decides how much margin the broker requires; it does not decide your risk. Your risk is set by the stop and the size, exactly as computed above. A trader using 500:1 leverage and a trader using 30:1 leverage with identical lot sizes and stops are risking identical amounts — the first one simply has more room to add positions before margin becomes binding, which is a hazard rather than a benefit. See the margin calculator for what the broker will actually hold.
Where a "lot" comes from
The 100,000-unit standard lot mirrors the exchange-traded contract sizes it grew up beside: CME's Euro FX future is 125,000 euro with a minimum fluctuation of 0.00005, worth $6.25 a contract.[1] Retail lot sizing is a convention on top of that structure.
The number is the easy part
Everything above is arithmetic, and anyone opening this page gets the same answer. What no calculator can settle is whether you took the trade on these terms, or are describing — afterwards — the version of it that worked out.
That is what a trade recorder is for: the trade committed before it resolves, timestamped and sealed on the spot, on a Merkle-anchored log a stranger can check without kappi's cooperation. The plan you typed here stops being a plan you remember having. $15/month, no free tier.
Sources
Frequently asked questions
How do I calculate lot size in forex?
Divide your dollar risk (account × risk %) by the stop distance in pips times the pip value per lot. The result is the number of standard lots.
What is a standard, mini and micro lot?
100,000, 10,000 and 1,000 units respectively — worth roughly $10, $1 and $0.10 per pip on a USD-quoted pair.
Does leverage change my position size?
No. Leverage determines the margin your broker holds, not your risk. Risk comes from lot size and stop distance, which is what this calculator sizes.
Why is pip value different on JPY pairs?
A pip on a JPY pair is 0.01 rather than 0.0001, and the quote currency must be converted back to your account currency. Use the pip value calculator to get the correct figure first.