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Position size calculator for stocks and forex

Enter your account size, risk %, entry and stop to get the exact number of shares or forex lots, the money at risk and the position value. Formula shown.

By the ChartFluent team · Updated

Position size = money at risk ÷ distance to the stop. Risk 1% of a $10,000 account ($100) on a stock bought at $50 with a stop at $48 ($2 a share): you buy 50 shares. In forex, divide by the stop in pips × the pip value: $100 ÷ (50 pips × $10) = 0.20 lots of EUR/USD.

Market
$

The money in the trading account, in US dollars.

%

Share of the account you accept to lose if the stop is hit.

$

The price you plan to buy (or sell short) at.

$

Below the entry for a long trade, above it for a short.

Position size50 shares

Money at risk
$100.00
Risk per share
$2.00
Exact size before rounding
50.00 shares
Actual risk (rounded size)
$100.00
Position value
$2,500.00
Share of the account
25%

Long (buy): the stop is below the entry

Position size formula

The calculator does three steps, the same ones you would do on paper.

  1. Money at risk = account size × risk per trade. $10,000 × 1% = $100.
  2. Risk per unit = the distance between your entry and your stop. For a stock, in dollars per share. For forex, in pips, multiplied by what one pip is worth for one lot.
  3. Position size = money at risk ÷ risk per unit, rounded down.

For stocks: shares = (account × risk %) ÷ |entry − stop|.

For forex: lots = (account × risk %) ÷ (stop in pips × pip value per lot), rounded down to 0.01 lot.

The result is always rounded down, never to the nearest number. Rounding 43.48 shares up to 44 would make the loss at the stop slightly bigger than the amount you decided to risk. That is why the calculator shows two lines: the money you chose to risk and the actual risk of the rounded position, which is equal or a little lower.

Worked example

Stocks: $10,000 account, 1% risk, buy at $42.50, stop at $40.20

  1. Money at risk: $10,000 × 1% = $100.00.
  2. Risk per share: $42.50 − $40.20 = $2.30.
  3. Shares: $100.00 ÷ $2.30 = 43.48, rounded down to 43 shares.
  4. Actual risk: 43 × $2.30 = $98.90, just under the limit. Position value: 43 × $42.50 = $1,827.50.

Forex: $10,000 account, 1% risk, EUR/USD from 1.1000 to a stop at 1.0965

  1. Money at risk: $100.00. Stop distance: 1.1000 − 1.0965 = 0.0035 = 35 pips.
  2. Pip value of one standard lot of EUR/USD: 100,000 × 0.0001 = $10.00.
  3. Lots: $100.00 ÷ (35 × $10.00) = 0.2857, rounded down to 0.28 lots (28,000 units).
  4. Actual risk: 0.28 × 35 × $10.00 = $98.00.

Yen pair: $5,000 account, 2% risk, USD/JPY from 150.00 to a stop at 149.50

  1. Money at risk: $100.00. Stop distance: 0.50 ÷ 0.01 = 50 pips (a yen pip is 0.01).
  2. Pip value of one lot: 100,000 × 0.01 = 1,000 yen, ÷ 150.00 = $6.67.
  3. Lots: $100.00 ÷ (50 × $6.67) = 0.30 lots (30,000 units), actual risk $100.00.

Stocks and forex: what changes

With stocks the unit is one share and the risk per share is simply the entry minus the stop. With forex the unit is a lot: a standard lot is 100,000 units of the base currency, a mini lot 10,000 (0.1) and a micro lot 1,000 (0.01). Most platforms accept steps of 0.01 lot, which is why the calculator stops there.

The stop distance in forex is counted in pips: 0.0001 for most pairs, 0.01 for pairs quoted in Japanese yen. A stop from 1.1000 to 1.0950 is 50 pips; a stop from 150.00 to 149.50 on USD/JPY is also 50 pips. What one pip is worth in dollars depends on the pair, which the pip calculator explains in detail. For pairs that are not quoted in US dollars, the calculator converts at the rate you type, because this site has no live prices.

Choosing the risk per trade

The calculator does not choose the percentage for you. Many risk-management guides use 1% to 2% of the account per trade. The reason is arithmetic, not a rule of the market: losses come in streaks, and a small fixed percentage keeps a streak survivable. At 1% per trade, ten losses in a row leave about 90% of the account; at 5%, about 60%; at 10%, about 35%. The risk/reward calculator has a table of how many losses in a row it takes to reach a given drawdown.

What position sizing does not do

  • It does not guarantee the loss. A stop order becomes a market order when the price is reached. If the price gaps past your stop (overnight news, earnings, a weekend in forex), the fill can be worse and the loss bigger than planned.
  • It does not make a trade good. It only fixes how much a wrong idea costs. Where the stop goes should come from the chart: the level where the idea is proven wrong, not a distance picked to get a bigger position.
  • It does not include costs. Commissions, spreads and swap fees add to the loss. Leave a margin for them.
  • A large position can need borrowed money. With a tight stop the share count can exceed what the account can pay for. The calculator warns you when the position is worth more than the account: that would need margin, which brings its own risk.

Common mistakes

  • Choosing the position size first and then placing the stop wherever the risk fits. The stop belongs where the chart says the idea is wrong; the size follows from it.
  • Using the account balance including open profits that are not realised.
  • Forgetting that a forex pip on a yen pair is 0.01, not 0.0001, which makes the stop look 100 times smaller or larger.
  • Moving the stop further away after entering, which silently increases the risk the position was sized for.

Frequently asked questions

How do you calculate position size?

Multiply your account size by the percentage you are willing to lose on the trade, then divide by the distance between your entry and your stop. With $10,000, 1% and a $2 stop, that is $100 ÷ $2 = 50 shares. Round down so the loss never exceeds your limit.

What is the 1% rule in trading?

It is a common risk guideline: never lose more than 1% of the account on a single trade. It does not limit the position to 1% of the account; it limits the loss if the stop is hit. The position itself can be much larger than 1% of the account.

How many lots should I trade with $1,000?

It depends on the stop, not on the account alone. Risking 1% of $1,000 is $10. With a 20-pip stop on EUR/USD, one standard lot would lose 20 × $10 = $200 at the stop, so the size is $10 ÷ $200 = 0.05 lot (5 micro lots). With a 50-pip stop it would be 0.02 lot.

Why round the position size down?

Because rounding up would make the loss at the stop larger than the amount you decided to risk. Rounding down keeps the actual risk equal to or just under your limit.

Does a stop-loss guarantee my maximum loss?

No. A stop order turns into a market order once the stop price is reached, and in a fast market or a gap it can be filled at a worse price. The calculated risk is the plan, not a guarantee.

Sources

Risk/reward calculatorRatio, break-even win rate and a losing-streak table.Pip calculatorPip value in dollars for 1, 0.1 and 0.01 lot.

Education only, not financial advice. The calculators do arithmetic on the numbers you type; they do not know the market and do not predict prices.