Stock Position Size Calculator
Work out how many shares to buy for a given risk and stop-loss.
Please note: For information only, not investment advice. Share prices can fall as well as rise and past performance does not predict future results.
What the Stock Position Size Calculator does
Position sizing sets the number of shares so that hitting your stop-loss costs a fixed, predetermined amount. A concentration cap then prevents any single holding dominating the portfolio, even when a tight stop would technically allow it.
Formula
Risk amount = Portfolio × Risk % ÷ 100Risk per share = Entry − Stop-lossShares = Risk amount ÷ Risk per shareCapped at: Portfolio × Max position % ÷ Entry price
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Portfolio value | selected currency | Yes | Accepts 0 or more. |
| Risk per position | % | Yes | — |
| Entry price | selected currency | Yes | Accepts 0 or more. |
| Stop-loss price | selected currency | Yes | Accepts 0 or more. |
| Maximum position size | % | Optional | Cap on any single holding as a share of the portfolio. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Currency.
- Enter Portfolio value, Risk per position, Entry price and Stop-loss price.
- Optionally add Maximum position size.
- Select Calculate.
Worked example
A $100,000 portfolio risking 1%, entering at $50 with a stop at $46.
- Portfolio
- 100000
- Risk
- 1
- Entry
- 50
- Stop
- 46
$1,000 ÷ $4 = 250 shares, a $12,500 position — 12.5% of the portfolio.
Frequently asked questions
Why cap position size if the risk is already fixed?
A very tight stop can mathematically justify an enormous position. If the stock gaps through the stop overnight, that position size becomes the real risk.