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Lot Size Calculator

Size every forex trade so it risks the same slice of your account. Enter your balance, risk percentage, stop loss and pip value, then press Calculate to see the position size in lots.

Written by TopicDrill Editorial Team·Updated June 2026

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Your trade

Set your account, risk and stop, then press Calculate.

$
$

Position size

0.4 lots

40,000 units

Cash at risk$100
Mini lots4
Micro lots40

Account exposure

1.0%at risk
Risked $100 Safe $9.9k

Lots by risk level

0.5%
0.2
1%
0.4
2%
0.8
3%
1.2
5%
2

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How the lot size calculator works

Position sizing turns a vague feeling about risk into a precise number of lots. The tool starts from the cash you are prepared to lose on the trade, found by applying your risk percentage to the account balance. It then asks how much one standard lot would lose if the stop were hit, which is the stop distance in pips multiplied by the pip value, and divides one by the other to get the lot size.

The donut shows what share of the account is exposed on this single trade, while the bars compare how many lots different risk levels would allow. Together they make it obvious how quickly position size grows as you loosen the stop or raise the risk percentage.

A quick example

With a $10,000 account, 1% risk, a 25 pip stop and a pip value of $10 per standard lot, you are willing to lose $100. One standard lot would lose 25 times 10, or $250, if the stop is hit. Dividing $100 by $250 gives 0.4 standard lots, which is 4 mini lots or 40 micro lots, and 40,000 units.

Things to keep in mind

The figure assumes your stop is honoured at the exact price. Slippage, gaps and widening spreads can push the real loss past the planned amount, so trade liquid pairs and avoid major news if you want the math to hold. For a primer on managing trading risk, see this risk management overview. To gauge the upside of a position, pair this with our profit margin calculator.

Frequently asked questions

What is a lot in forex trading?

A lot is a standard unit of trade size. One standard lot is 100,000 units of the base currency, a mini lot is 10,000 units and a micro lot is 1,000 units. Lot size decides how much each pip of price movement is worth, so it directly controls how much you win or lose per trade.

How is the correct lot size calculated?

First the calculator finds the cash you are willing to lose, which is your account balance times your risk percentage. It then divides that by the loss one standard lot would take if your stop loss were hit, which is the stop distance in pips times the pip value per lot. The answer is the position size in standard lots.

Why risk a fixed percentage on each trade?

Risking the same small percentage, often one or two percent, keeps any single loss from doing serious damage to the account. Because the percentage is applied to the current balance, your position sizes shrink after losses and grow after wins, which protects capital during a losing run.

What is the pip value per lot I need to enter?

It is the cash value of a one pip move for one standard lot of the pair you trade. For most pairs quoted against the US dollar this is about ten dollars per standard lot. For pairs where the dollar is not the quote currency the value differs, so check your broker for the exact figure.

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