Tools · Calculator
Position size calculator
Work out a holding as a percent of a portfolio, or the dollar amount and share count that match a percent you choose.
Arithmetic, not advice. This calculator turns a share count, a price and a portfolio total into a percent, and a percent into a dollar amount. It doesn't say how large a position is right for anyone.
The formula
Position value = share price × number of shares
Share of the portfolio = position value ÷ portfolio value × 100
Dollars for a chosen percent = portfolio value × percent ÷ 100
A worked example
80 shares at 50 are worth 80 × 50 = 4,000. In an 80,000 portfolio that is 4,000 ÷ 80,000 × 100 = 5%. Ten percent of the same portfolio is 80,000 × 0.10 = 8,000, which is 8,000 ÷ 50 = 160 shares at that price.
The dollar-cost averaging calculator shows how a repeated purchase of a fixed dollar amount builds a share count over time.
Common questions
What is a position's share of a portfolio?
The position's value divided by the portfolio's value, as a percent. 4,000 in an 80,000 portfolio is 5%.
How do I find the dollars that equal a percent of the portfolio?
Multiply the portfolio value by that percent. 10% of 80,000 is 8,000. Divide that amount by the share price to get the matching share count.
Does this tell me how large a position is right for me?
No. The calculator only does the arithmetic on numbers you enter. It doesn't consider risk, diversification, taxes or anyone's circumstances, and it isn't a recommendation.
What if the position is larger than the portfolio?
The percent comes out above 100. That can happen if the portfolio total is missing part of the position, or if the figures are from different dates. The calculator still reports the ratio.
Can I leave the percent field blank?
Yes. You'll still see the position value and its share of the portfolio. The last two results fill in once you type a percent.
Disclosures
- Editor holdings
- The editor holds no position in any company named on this page. As of Nov 11, 2026.
- Compensation
- Nobody paid for this calculator. No affiliate links on this calculator.
- Sources
- Each company's own SEC filings, linked next to each number.
- Last updated
- Nov 10, 2026
General education, the same for every reader. Not a recommendation to buy, sell or hold any security, and it doesn't consider your situation.
More in Learn and Tools · Methodology & Disclosures explains where every number comes from.