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Position size calculator
Position size = (account × risk %) ÷ (entry − stop). Enter your numbers and it tells you how many shares or contracts keep a losing trade inside your own rule.
Size
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Dollars at risk
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Position value
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Share of account
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Sizing is only half of it. The other half is taking the stop when price gets there. Get early access and score yourself on it every day.
The formula
Position sizing turns a vague intention (“don’t lose too much”) into a number you can check before you click buy.
risk per unit = |entry − stop| × multiplier
size = floor(risk budget ÷ risk per unit)
The multiplier is 1 for shares and ETF units and 100 for a standard listed options contract. Round down, never up: rounding up quietly breaks the rule you just wrote.
Worked example
Your account is CA$20,000 and your rule is to risk 1% per trade, so your risk budget is CA$200. You plan to buy a Canadian-listed stock at $50.00 with a stop at $48.50, which is $1.50 of risk per share.
CA$200 ÷ $1.50 = 133.3, so the size is 133 shares. If the stop is hit, the planned loss is 133 × $1.50 = CA$199.50. The position is worth $6,650, about 33% of the account.
Same trade on a US-listed stock with a rate of 1.37 CAD per USD: the budget becomes US$145.99, and the size drops to 97 shares. That exchange-rate step is the one most calculators skip.
Why the stop comes first
Size depends on the stop, not the other way round. Pick the price where your idea is wrong, then let the calculator tell you the size. Moving the stop to fit a bigger position is one of the most common ways traders break their own rules. We wrote about it in how to stop revenge trading and how to calculate position size.
Questions
How do I calculate position size?
Multiply your account size by the percent you are willing to risk to get your risk budget. Divide that by your risk per share (entry minus stop). Round down to a whole number of shares.
What percent of my account should I risk per trade?
Many traders write a rule between 0.5% and 2% per trade. The calculator does not pick a number for you; it applies the rule you set. Educational only, not financial advice.
My account is in CAD but the stock trades in USD. What do I enter?
Choose CAD for the account and USD for the stock, then enter the exchange rate you would actually get (CAD per 1 USD). The calculator converts your risk budget before sizing.
Does it work for options?
Yes. Choose Options contracts: enter the premium you pay and the premium where you would exit. Each listed contract usually covers 100 shares, so the risk per contract is the difference times 100.
Does it include commissions or slippage?
No. Stops can fill worse than planned, especially on gaps. If you pay commissions, subtract them from your risk budget first, or size slightly smaller.
Educational only, not financial advice. The calculator does arithmetic on the numbers you enter; it does not know the market, your broker’s fills, or whether a trade is a good idea. Want a check on whether you kept last week’s rules? Try Rule Check.
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