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Position size calculator
Balance, risk, stop distance in, lot size out. It gets crosses, metals and indices right, it shows the conversion rather than hiding it, and it rounds down— so the size it gives you never risks more than the number you set.
The formula
Risk budget = balance × risk %
Lots = risk budget ÷ (stop distance × value of one pip on one lot)
- Stop distance — in pips for currency pairs, in points for everything else, measured from entry to stop.
- Value of one pip on one lot — in your account currency, which is where the whole difficulty lives. See the pip value calculator for the three conversion cases.
- Then round down to your broker's lot step. Never up.
Everything hard about position sizing is in the second line. The division itself is trivial; getting the pip value right for a cross, or for gold, is not — and a wrong pip value produces a wrong size with no visible symptom until the loss arrives.
Six worked cases
All on a 10,000 USD account. Prices are illustrative — this page fetches nothing — and every row is computed by the same code the calculator runs.
| Instrument | Risk | Stop | Pip / point value | Exact | Size | Actually risks |
|---|---|---|---|---|---|---|
| EUR/USD The easy case: the pip is already in your account currency. | 1% 100.00 USD | 20 pips | 10.00 USD | 0.50 | 0.50 lots | 100.00 USD |
| USD/JPY Base-currency pair — the pip value, and so the size, moves with the price. | 1% 100.00 USD | 25 pips | 6.36 USD | 0.6288 | 0.62 lots | 98.60 USD |
| GBP/JPY A JPY cross. The size depends on USD/JPY, not on GBP/JPY. | 1% 100.00 USD | 40 pips | 6.36 USD | 0.393 | 0.39 lots | 99.24 USD |
| EUR/GBP Cross with neither leg in the account currency — needs a rate. | 0.5% 50.00 USD | 15 pips | 12.70 USD | 0.2625 | 0.26 lots | 49.53 USD |
| Gold (XAU/USD) Gold, in points: a 300-point stop is a $3.00 move. | 1% 100.00 USD | 300 points | 1.00 USD | 0.3333 | 0.33 lots | 99.00 USD |
| US30 / Dow (CFD) An index CFD, 120 index points of stop. | 1% 100.00 USD | 120 points | 1.00 USD | 0.8333 | 0.83 lots | 99.60 USD |
What the number is actually for
Position size is the decision that determines the shape of an account. Entry technique gets the attention; sizing does most of the damage, and it is the only input a trader fully controls. Two traders taking identical trades with identical stops can end a year in completely different places purely on this number.
Sizing from risk rather than from habit also makes your results comparable. Once every trade risks the same fraction, a result can be expressed in R-multiples and a $500 win on a small position stops looking like the same thing as a $500 win on a large one.
The thing this calculator cannot check is whether the risk percentage itself is sane — that is the risk-per-trade question, and the arithmetic of losing streaks there is more sobering than most people expect.
Questions
Why does it round down instead of to the nearest lot?
Because rounding up increases the risk above the number you just typed in. If the exact answer is 0.567 lots and your broker takes two decimals, 0.57 risks slightly more than your limit and 0.56 risks slightly less. A tool whose job is to keep you inside a risk limit should never hand you a size that breaks it, however small the excess. The page shows the exact figure too, so the choice is visible rather than hidden.
Should the stop distance include the spread?
For a sell stop on a long position, yes — you exit at the bid, so a stop measured from the ask is optimistic by roughly one spread. On a 20-pip stop with a 1-pip spread that is 5% more risk than you calculated. Add the spread to your stop distance if you want the number to be exact, and remember that spread widens exactly when stops get hit.
What about commission and swap?
Neither is in this calculation, and both are real. Commission is charged whether the trade wins or loses, and swap accrues on anything held overnight — so a stopped-out trade costs slightly more than the stop distance suggests. For most position sizes it is a rounding error against a 1% risk; for high-frequency, tight-stop trading it is not, and your statement is where you find out which one you are.
What size were you actually trading?
Your MT4 or MT5 statement records the size of every position you have ever closed. The gap between the size this calculator gives you and the sizes in that file is the honest measure of how consistently you size. No signup, no upload — the file is parsed inside your browser tab.
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