Position Size Calculator
Work out how many shares, units or lots to trade from your account size, risk per trade and stop-loss distance.
Fill in your account balance, entry price and stop-loss — the position size is calculated as you type.
- Position size (units)
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- Whole units (rounded down)
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- Amount at risk
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- Risk per unit
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- Position value
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- Position as % of account
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- Margin required
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- Reward : risk
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- Potential profit at target
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Educational tool, not financial advice. It ignores commissions, spread, swap, slippage and gaps — a real fill can be worse than your stop-loss price, so the loss can exceed the number shown.
How it works
This calculator uses the standard fixed-fractional (percent-risk) position
sizing method used by most trading plans. First it works out the cash you are willing to lose:
risk amount = account balance × risk %. Then it measures the distance from your
entry to your stop-loss, risk per unit = |entry − stop|. Dividing one by the other
gives the position size: units = risk amount ÷ risk per unit. With a
$10,000 account, 2% risk, an entry of $50 and a stop at $48 that is $200 ÷ $2 = 100 shares,
a $5,000 position — half the account, even though only $200 is actually at risk.
From there it shows the notional position value, what share of your account that is, the margin
you would need at the leverage you enter (margin = position value ÷ leverage), and —
if you add a take-profit — the reward-to-risk ratio
(|target − entry| ÷ |entry − stop|) plus the profit that target would produce. It
works for long and short trades and for anything quoted per unit: shares, crypto, CFDs or forex
lots. Everything is plain arithmetic done in your browser: no account, no ads, and your numbers
never leave the device.
Frequently asked questions
How is position size calculated?
This calculator uses fixed-fractional (percent-risk) sizing. First it works out the cash you are willing to lose: account balance × risk %. Then it divides that by the distance from entry to stop-loss: units = risk amount ÷ |entry − stop|. With a $10,000 account, 2% risk, an entry at $50 and a stop at $48, that is $200 ÷ $2 = 100 shares, a $5,000 position with only $200 truly at risk.
What is the 2% rule in trading?
The 2% rule says you should never risk more than 2% of your account balance on a single trade, so a run of losers cannot wipe you out. Many traders use 1% or less. Enter your figure in the risk field — or switch to a fixed cash amount if you prefer to think in money rather than percentages.
Does it work for short trades, forex and crypto?
Yes. Switch the direction to Short and the calculator expects the stop-loss above your entry and the take-profit below it. Because the maths is per unit, it works for anything quoted per unit — shares, crypto coins, CFD contracts or forex lots — as long as your entry, stop and balance are in the same currency. Fees, spread, swap and slippage are not included.