Portfolio concentration: measure top holdings and test a simple shock

Concentration means that a small number of exposures can strongly influence a portfolio's outcome. Counting stock names is a weak substitute for measuring it. A portfolio with twenty names can still depend heavily on one company, one sector, or one shared economic driver.

This guide shows descriptive measures and a deliberately simple stress scenario. It does not set a suitable position limit for you. Appropriate exposure depends on objectives, resources, time horizon, and risks that a holdings table may not capture.

Measure weights using a stated scope

For each position, divide current market value by the total current value of the included portfolio. Rank the results from largest to smallest. The largest-position weight and the sum of the top three are easy to explain and audit.

Use current value when asking what a price move would affect now. Cost-based weights instead describe where purchase money was deployed. Exclude neither unknown classifications nor inconvenient losers just to make the portfolio appear more balanced. Record whether funds, cash, and other accounts are included.

Worked example: six names, one dominant position

Take a fictional portfolio with current value of ₹3,00,000:

Holding	Current value	Weight
Summit Bank	₹1,20,000	40%
Valley Software	₹60,000	20%
Grove Finance	₹45,000	15%
Prairie Foods	₹30,000	10%
Harbor Energy	₹30,000	10%
Orchard Health	₹15,000	5%
Total	₹3,00,000	100%

The largest position is 40%. The top three total ₹2,25,000, or 75%. If Summit Bank and Grove Finance are both grouped under financial services, that sector totals ₹1,65,000, or 55%.

These are three different views of the same portfolio. Six distinct names did not prevent one stock from representing two-fifths of the money or one broad sector from representing over half. The figures describe exposure; they do not establish that a particular company is likely to fall.

Test a clearly labelled hypothetical shock

Assume Summit Bank falls 25% while every other price stays unchanged, with no trades, fees, or dividends. Its value falls from ₹1,20,000 to ₹90,000. The portfolio loses ₹30,000 and becomes ₹2,70,000—a 10% portfolio decline.

The shortcut gives the same answer: 40% initial weight × 25% assumed decline = 10% portfolio impact. After the move, Summit's weight is ₹90,000 ÷ ₹2,70,000 = approximately 33.33%. A lower weight here reflects a loss, not a diversification action.

For a separate scenario, assume both financial-services holdings fall 20%, and all others stay flat. The loss is 20% × ₹1,65,000 = ₹33,000, or 11% of the portfolio. Do not add these two scenario losses together: they are alternative assumptions and both involve Summit Bank.

Look beyond the visible categories

Companies in different sectors may depend on the same export market, commodity input, or refinancing conditions. A sector chart cannot measure all correlations. Similarly, an employer's shares and employment income may expose a household to one business in ways that the broker account does not show.

Funds can overlap with direct stocks. Zerodha's portfolio analytics discussion explains that underlying fund holdings may repeat direct exposures. Quantifying that overlap requires dated underlying data; do not infer it from a fund name or assume the extension automatically supplies it.

Turn a number into a documented question

Write down which exposure dominates, what evidence supports its classification, and what the stress assumption excludes. Ask how a loss would affect planned cash needs. A scenario with other prices held constant is a sensitivity test, not a probability forecast or a worst-case bound.

No percentage here is a universal cap, and a warning should not become an automatic trade instruction. Selling, adding money elsewhere, or doing nothing have different costs and consequences that this arithmetic does not evaluate.

Use HoldingsTracker Pro's current insights to inspect breakdowns, the concentration feature page to understand scope, and pricing to check access. Explore the fictional portfolio demo to see position and sector weights. The extension has no historical concentration series or automatic rebalancing capability. Continue with sector allocation and the holdings review workflow to check denominators and inputs. HoldingsTracker Pro is independent of Zerodha. This is educational documentation, not personalised investment recommendations or tax advice.