Position Sizing Calculator
Find how many shares fit your account risk budget and available cash at a planned entry and stop.
Check what one more trade increment would cost and risk.
Modeled position size
Enter your trade assumptions or load the worked example.
Actual loss may exceed the modeled loss if the fill differs from the stop price. This scenario excludes transaction charges and leverage.
Learn to size a stock trade
Compare worked trades limited by risk or cash, and see how whole-share increments affect the result.
Read the position sizing guideFormula and methodology
Shares = trade increment × smaller of the risk-limited and cash-limited whole blocks.
Shares = I × min(floor(B ÷ (I × D)), floor(C ÷ (I × E))). I is the share increment, B is equity times risk percentage divided by 100, C is available cash, E is entry and D is the positive distance from entry to stop. The result checks the next increment against both limits.
Definitions
Account equity determines the monetary risk budget. Available cash is the amount allocated to buy shares. The stop distance is entry minus stop per share. The trade increment is the number of shares in each permitted block.
Verified worked examples
With 10,000 in equity and cash, 1% risk, entry 50, stop 48 and an increment of one share, the risk budget is 100 and the distance is 2. The model allows 50 shares costing 2,500 with a modeled loss of 100. One more share raises modeled loss to 102.
Interpretation
The next-increment message shows which limit or limits would be exceeded. Unused risk is the risk budget minus the modeled loss, and unused cash is available cash minus the entry cost. Zero shares means no complete increment fits both limits.
Inputs and interpretation
Choose a display currency. Enter account equity, cash available for this trade, a risk percentage, per-share entry and stop prices, and the number of shares per increment. Enter an explicit zero where applicable. Use a stop below entry.
Assumptions and limitations
One cash-funded long stock entry and hypothetical exit at the stop price, with consistent major-currency units. USD, GBP, CAD, AUD and INR change display formatting only. Convert quotes in pence to pounds before mixing them with GBP amounts.
Supported domain and common mistakes
Equity, cash and prices support up to 1 trillion with up to 12 decimal places. Entry must be positive and the stop may be zero. Risk ranges from 0% to 100%. Share increments are positive whole numbers up to 1 trillion. Calculations preserve exact decimals before displaying money to cents.
Do not substitute total account equity for cash you can allocate. A tighter stop can increase the risk-based quantity while the cash limit remains unchanged.
Frequently asked questions
How many shares can I buy for my chosen risk?
Can I enter a zero stop price?
Why does the next increment exceed both limits?
Why is the result zero shares?
Does changing currency convert the prices?
Can I use the calculator for short selling?
Sources and educational scope
Educational scenario. Actual fills and losses may differ from the estimate. The model excludes fees, taxes, spreads, slippage, gaps, FX, short positions, leverage and broker order rules. It provides no personalized investment advice.
Reviewed . AI-assisted content under operator editorial responsibility. No independent expert financial review is claimed.