Portfolio Concentration Risk Calculator
Largest holding as share of portfolio.
Calculate portfolio concentration risk: largest holding as percentage of total portfolio value. Enter portfolio total and see the result instantly.
What this tool does
Enter portfolio total and largest holding. The tool shows concentration percentage and residual diversification.
Enter Values
Formula Used
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Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
Concentration risk lives in the top holding. A 200,000 portfolio with a 60,000 single stock is 30% concentrated — one stock's bad year can drop the whole portfolio 10-15%. Most advisors flag concentration above 20% and serious advisors above 10%. Company shares from employer grants are a common concentration source — tax-efficient to hold but carry the concentration risk.
A worked example
Try the defaults: portfolio total of 200,000, largest single holding of 60,000. The tool returns 30.00%. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.
What moves the number most
The result responds to Portfolio Total and Largest Single Holding. The rate and the time horizon usually dominate — compounding means a small change in either reshapes the final figure more than a similar shift in contribution size. Test this by doubling one input at a time.
The formula behind this
Largest holding value divided by total portfolio value. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.
Using this well
Treat the output as one point on a wider map. Run it three times — a pessimistic case, a central case, and a stretch case — and plan against the pessimistic one. That habit alone separates people who stick with an investment plan from those who bail at the first wobble.
What this doesn't capture
Steady-rate math ignores real-world volatility. Actual returns are lumpy; sequence-of-returns risk matters most in drawdown; fees and taxes drag on compound growth; and behaviour changes in drawdowns can reduce outcomes below the projection. Treat the number as one scenario, not a forecast.
Portfolio concentration produces a percentage based on the inputs provided.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
Largest holding value divided by total portfolio value.
References
Frequently Asked Questions
What's a safe concentration level?
What if it's an index fund?
Employer stock concentration?
How to reduce concentration?
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