How to spot portfolio concentration risk

1. Use current values to calculate weights

For a simple unleveraged portfolio, divide each holding’s current market value by the total value of the portfolio you are reviewing. Use a common currency and a consistent valuation date. Decide whether your scope includes cash, funds and other accounts, and state that scope.

A holding worth €2,500 in a €10,000 portfolio has a 25% weight. If the same holding sits in a second account, a combined review should include both positions. Purchase cost answers a different question from current exposure. Borrowing, derivatives and short positions require more than this simple calculation.

2. Look beyond individual companies

Group holdings by sector, then investigate other connections: similar customers, suppliers, regions or financing conditions. A sector label is a useful starting point, not proof that every company in the group behaves identically.

Concentration can also grow as one investment outperforms the others. FINRA highlights the need to look across correlated holdings and overlapping fund investments, not only the number of securities owned. Read FINRA’s concentration-risk guide.

3. Test the arithmetic with a small example

Imagine five fictional holdings, each worth €2,000. Three share a technology-sector classification. The other two belong to different sectors. This is an arithmetic illustration, not a suggested allocation.

If the technology holdings all fall 10% and everything else stays unchanged, they lose €600. The portfolio falls from €10,000 to €9,400: a 6% decline.

This calculation holds the other positions unchanged and excludes fees, taxes, currency moves and trading. It is not a forecast, loss limit or probability estimate. Real holdings may move together or in opposite directions, and their weights change as prices change.

4. Look inside funds where information is available

A direct holding and a fund can expose you to the same company. In another invented example, suppose a company is 10% of your portfolio directly. You also place 40% of the portfolio in a fund that holds 5% in that company. The fund contributes an additional 2% exposure, making the combined estimate 12%.

Use dated fund holdings and avoid counting the same underlying position twice. This is a simplified look-through estimate; incomplete disclosures, derivatives and changing fund positions can make the result less precise. This guide’s fund calculation is a manual research example, not a claim that TradinZ automatically calculates fund overlap.

5. Turn the result into questions

Scope

Which accounts, assets, currencies and dates are included?

Largest positions

How much depends on the largest company and largest sector?

Shared dependencies

Could one customer, region or economic change affect several holdings?

Missing information

Which fund holdings or exposures have not been verified?

Review trigger

Which price move, new holding or report would make you revisit the calculation?

There is no universal “safe” concentration percentage for every investor. Diversification can reduce concentration risk, but it cannot eliminate investment losses. Decisions about changes depend on your circumstances, goals and constraints. Investor.gov explains asset allocation and diversification.

Explore a portfolio in context

TradinZ Portfolio X-Ray connects holdings with available company context and descriptive exposures. Try the free five-stock example; it is labelled illustrative and contains no personal account data. Your own holdings and personal workspace require Pro.

For the next layer of research, read how to research the businesses behind your holdings and check the methodology and data limitations.