Lot Size Calculator

This position size calculator starts where careful traders start: with the maximum you are prepared to lose if the trade fails. Enter your account balance, the percentage you are willing to risk, the pair, its price and the distance to your stop-loss in pips. The result is the position size, in units and lots, that makes a stopped-out trade cost roughly that amount.

The formula

Pip value per lot is $10 for pairs quoted in US dollars; for other pairs it depends on the exchange rate, which the calculator handles for you.

Worked example (illustrative numbers)

A trader with an $8,000 balance decides to risk 1.5% on a EUR/USD trade, with a stop-loss 40 pips from the entry price.

• Risk amount: $8,000 × 1.5% = $120.
• Loss per lot if stopped: 40 pips × $10 = $400.
• Position size: $120 ÷ $400 = 0.3 lots (30,000 units).

If the stop needed to be 60 pips away instead, the same $120 risk would allow only 0.2 lots. The stop is set by where the trade idea is proven wrong; the position size then adjusts to fit your risk, not the other way round.

Using the position size calculator result

Treat the answer as a maximum. Round down to the nearest size your provider allows, because rounding up quietly increases the risk. Costs are not included, so a stopped-out trade will lose slightly more than the risk amount once spread and commission are added; see trading fees explained.

A stop-loss can fill beyond its level when prices gap, so the actual loss on a bad day may exceed the plan. Check the margin the position requires with the margin calculator; if it ties up most of your balance, the position is too large for the account even if the risk figure looks small.

Many educational sources suggest risking only a small percentage of an account on each trade, because a run of losses is normal. At 1.5% per trade, ten consecutive losses would cost roughly 14% of the starting balance, which is survivable; at 10% per trade, the same run would leave only about a third of the account.