Forex Position Size Calculator
Calculate the lot size that risks exactly your chosen percentage on a given stop.
Please note: Forex trading carries a high risk of loss, amplified by leverage. Exchange rates must be entered manually — no live market data is used.
What the Forex Position Size Calculator does
Forex position sizing works backwards from risk, exactly as in other markets: fix the amount you can lose, measure the stop in pips, and solve for the lot size that makes those two match.
Formula
Risk amount = Account × Risk % ÷ 100Units = Risk amount ÷ (Stop in pips × Pip size × Conversion rate)Standard lots = Units ÷ 100,000
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Account balance | selected currency | Yes | Accepts more than 0. |
| Risk per trade | % | Yes | — |
| Stop-loss distance | pips | Yes | Accepts more than 0. |
| Pip size | one of 3 options | Yes | — |
| Quote → account currency rate | number | Yes | Accepts more than 0. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Pip size and Currency.
- Enter Account balance, Risk per trade, Stop-loss distance and Quote → account currency rate.
- Select Calculate.
Worked example
A $10,000 account risking 1% with a 25-pip stop on a USD-quoted pair.
- Account
- 10000
- Risk
- 1
- Stop
- 25
- Conversion
- 1
$100 risk ÷ (25 × $0.0001) = 40,000 units, or 0.40 standard lots.
Reading the result
- "Amount at risk" and "Loss if stopped out" should match — they are the same number by construction, restated two ways as a sanity check. If a broker rounds your lot size down to the nearest 0.01, the realised risk will be a little lower than the target; rounded up, a little higher.
- The units/lots figures are all the same position expressed at different scales — 40,000 units, 0.40 standard lots and 4.0 mini lots are one trade, not three options. Pick whichever unit your broker quotes in.
Assumptions and limitations
- The conversion rate is whatever you enter, held fixed for the trade — it does not update live, so a stale rate on a cross pair will throw off the risk amount slightly.
- Pip size is a single fixed value for the whole calculation. It does not know which pair you are trading, so it has to be told.
Common mistakes
- Using 0.0001 as the pip size on a JPY pair, where a pip is 0.01. That is a 100x error in the opposite direction — the position size comes out a hundred times too small.
- Sizing the position and then letting spread or slippage widen the real entry-to-stop distance beyond the pips entered here, which quietly increases the actual risk past the target percentage.
Frequently asked questions
Does leverage change my position size?
No. Leverage determines how much margin the position ties up, not how much you risk. Risk is set by your stop distance and lot size.
What if the calculated lot size is below the broker minimum?
Either widen the stop, accept slightly more risk on the minimum size, or trade a broker offering micro or nano lots.