VOO and VTI Together: Measuring Portfolio Overlap
Measure shared holdings, combined company weights and what each new purchase adds.
Reviewed October 5, 2026 · Original hypothetical examples in USD
VOO and VTI together can look like a more diversified portfolio because there are two fund names on the statement. The useful question is what those names represent. Both supply U.S. stock exposure, and many large companies appear in both. Adding VOO to VTI generally increases the emphasis on their shared large-company holdings.
That combination can have a practical purpose. You might have accumulated different funds in separate accounts, or deliberately prefer a blend between a large-company benchmark and the broader market. What deserves measurement is the resulting allocation, rather than whether owning two tickers is inherently good or bad.
This guide builds a repeatable overlap worksheet. We will distinguish a count of shared securities from their portfolio weights, calculate a combined company exposure, examine a hypothetical large-company sleeve and test what a new contribution changes. All numerical holdings examples are invented; they are not measurements of current Vanguard portfolios.
Start with the exposure each fund supplies
VOO follows the S&P 500, a benchmark of leading large U.S. companies. VTI follows a total-market benchmark that includes a broader range of U.S. company sizes. Vanguard’s current materials use the Morningstar US Total Market Index name for VTI; older materials refer to CRSP. Use current documents and their dates when building a worksheet.
A broader universe does not mean that each company receives an equal investment. Size-weighted indexes can give the largest businesses substantial influence while assigning small individual weights to many other holdings. The additional businesses increase breadth, but the percentage of invested dollars outside the large-company group still matters.
Imagine a fictional market with twenty large businesses collectively worth $850 billion and eight hundred smaller businesses collectively worth $150 billion. A simple size-weighted portfolio would allocate 85% to the first group. The smaller businesses would dominate the company count while representing only 15% of capital.
This distinction explains why a statement such as “VTI owns thousands of stocks” cannot settle the overlap question. It tells you something about breadth; it does not tell you how much your combined portfolio relies on the largest companies. Neither domestic stock fund supplies a complete allocation across countries, bonds and cash.
Three overlap measures answer different questions
The first measure is a count: how many securities appear in both lists? Match identifiers carefully. Company names can differ across files, tickers can change, and different share classes can belong to the same business. Decide whether your worksheet measures individual securities or companies before comparing the lists.
The second measure is directional coverage: what percentage of Fund A is invested in securities also held by Fund B? The reverse percentage can differ. A small set of holdings might all appear inside a larger fund, while the larger fund owns many securities absent from the smaller one.
The third measure is weighted overlap between two complete fund portfolios. One common calculation adds the smaller of the two weights for every matching security. This produces a symmetric measure when the same universe, identifiers and weight conventions are used. It does not tell you your personal combined holding weights.
| Security | Fund A | Fund B | Smaller shared weight |
|---|---|---|---|
| Company Alpha | 60% | 40% | 40% |
| Company Beta | 40% | 30% | 30% |
| Company Gamma | 0% | 30% | 0% |
Both A securities appear in B, so 100% of A’s weight is in shared securities. Only 70% of B’s weight is in shared securities. The symmetric minimum-weight measure is 70%. All three statements can be correct because they describe different relationships.
A 50/50 personal allocation to these fictional funds would instead hold 50% Alpha, 35% Beta and 15% Gamma. Those are the weights needed to assess the investor’s exposure. They are calculated by blending fund weights, rather than by substituting the overlap percentage for a company’s actual allocation.
Keep these measures in separate worksheet columns. A single “overlap” number without a definition invites misunderstandings. In particular, high common-holdings coverage does not mean two funds must have identical weights, risk or returns.
Build a holdings worksheet you can reproduce
Download complete holdings from the providers and record the holdings date, retrieval date and source. Prefer matching holdings dates. A list updated today and a list from several weeks ago can differ because of price changes or index maintenance rather than because of a persistent strategy difference.
Retain the original files. Create a separate working table containing security identifier, company name and weight in each fund. Normalize percentage formats: a spreadsheet cell containing 0.06 as a fraction and a cell containing 6 as percentage points represent the same 6% only after appropriate conversion.
Check that each complete fund list totals approximately 100%, with any small difference explained by rounding, cash or other positions. A top-ten table is useful for investigating major exposures, but it cannot establish full weighted overlap. Missing holdings should not silently become zero-weight securities.
Combine alternate share classes only if your objective is company-level concentration, and document that choice. If your objective is security-level overlap, keep them separate. Apply the same rule to both lists; otherwise the apparent difference can be created by your data preparation.
Then compute the combined weight for each row and rank the resulting portfolio. Look at the top positions, sectors and company-size groups. This turns a research exercise into an allocation review: you can see where the dollars end up and decide whether that matches the purpose of the holding.
Calculate one company across both funds
Suppose a fictional household has $24,000 in VOO and $16,000 in VTI. Those positions represent 60% and 40% of its $40,000 two-fund stock sleeve. Assume an invented company weight of 6% in VOO and 5% in VTI.
VOO contributes $1,440 of company exposure: $24,000 multiplied by 6%. VTI contributes another $800: $16,000 multiplied by 5%. The combined $2,240 is 5.6% of the $40,000 sleeve. Owning the company indirectly through two funds does not divide that exposure in half.
The percentage depends on the denominator. If the household also has $10,000 in cash, the same $2,240 represents 4.48% of its $50,000 total portfolio. If it holds $2,000 of that company directly as well, both the numerator and the total portfolio value must be updated.
For that last case, total company exposure becomes $4,240 and total assets become $52,000, making the company approximately 8.15% of the stated portfolio. The fund-only worksheet would miss this larger concentration unless the direct holding was explicitly included.
The calculator below deliberately measures only the two-fund sleeve. Use it for a selected company or consistently defined group; include other holdings separately when assessing your overall finances. An accurately labeled limited calculation is more useful than a wider-looking number with omitted accounts.
A blend can reduce the broader-market portion
Use a different invented example to assess company-size exposure. Assume VTI allocates 85% to a selected large-company group and 15% outside it. Assume VOO allocates 100% to that same group. These are scenario inputs, not current fund facts or a claim that the portfolios are perfectly nested.
A 50/50 blend then has 92.5% in the group: half of 100%, plus half of 85%. Its remaining allocation is 7.5%. Holding both has moved the sleeve toward the shared large-company exposure and reduced the relative weight of the broader-market remainder.
A 75% VOO and 25% VTI blend has 96.25% in the group. A 25% VOO and 75% VTI blend has 88.75%. Those outcomes show how the allocation decision changes the result even though the fund names remain the same.
You can also solve for a target. Under these invented assumptions, achieving a 90% group weight requires approximately one-third VOO and two-thirds VTI. The equation is 90 = allocation × 100 + (1 − allocation) × 85, where the allocation is expressed as a fraction.
This is arithmetic rather than an allocation recommendation. Real holdings, group definitions and fund implementation can differ. Check that your group means the same thing in both datasets; a provider’s “large cap” label and another provider’s classification may use different thresholds.
VOO and VTI together: exposure calculator
Measure a company or a defined group
Formula: combined weight = VOO allocation × VOO holding weight + remaining allocation × VTI holding weight. Inputs are hypothetical and update automatically. This is a selected-exposure calculator, not a live or full-fund overlap scanner. No market returns, taxes, trades or other accounts are modeled.
Test what a new contribution actually adds
Return to the $24,000 VOO and $16,000 VTI household. Suppose it contributes $10,000 entirely to VTI, with no intervening price movement. The positions become $24,000 and $26,000, making VOO 48% of the new $50,000 sleeve and VTI 52%.
With the same invented 6% and 5% company weights, company exposure becomes $1,440 plus $1,300, or $2,740. Its percentage falls from 5.6% to 5.48%, even though the dollars allocated to the company increase. A lower concentration percentage is not the same thing as a smaller dollar position.
Under the separate 100% and 85% large-company group assumptions, the new group weight is 48% × 100% + 52% × 85% = 92.2%. Only $1,500 of the new $10,000 contribution reaches the hypothetical outside group. The rest increases shared large-company exposure.
This observation helps distinguish a contribution plan from a diversification objective. If the objective is meaningfully different exposure, verify what the next fund purchase adds before placing the order. A second ticker can be convenient without supplying the exposure change you had in mind.
Turn the worksheet into a portfolio review
Write down why the blend exists. A deliberate large-company emphasis, a gradual transition, broker restrictions and holdings accumulated across accounts are all different explanations. Each points to a different review question. The worksheet should support that question rather than imply that every overlap requires a sale.
Check your other accounts before deciding the blend is appropriate. A workplace fund, individual stocks or another broad-market ETF can repeat the same businesses. A detailed calculation confined to one account can still understate concentration across the household.
Keep implementation costs beside any proposed change. Selling may incur commissions, spreads, currency charges or account-specific tax consequences. These depend on the actual account and jurisdiction. A modest improvement in a chosen weight does not automatically justify all transaction costs.
Consider future contributions separately from existing positions. Where contributions are permitted, new purchases can move an allocation gradually. Where they are restricted, the plan may depend on available cash, distributions or trades. Whole-share rules can leave a small cash balance that should remain in the portfolio denominator.
Review on a practical schedule and when a material circumstance changes. Preserve the previous worksheet so you can distinguish a market-driven weight change from a deliberate allocation change. Constantly changing the blend after short performance comparisons can add costs without addressing the original exposure objective.
Common questions about VOO and VTI together
Does holding both automatically improve diversification?
No. Their shared holdings mean the result depends on weights and the rest of the portfolio. The blend can emphasize large companies compared with VTI alone. Calculate the selected exposures before describing what the extra fund adds.
Is owning both necessarily a problem?
No. A practical or deliberate reason can explain the arrangement. Investigate whether it serves the desired exposure and whether simplifying it would justify the associated costs.
Can the calculator give the current full overlap percentage?
No. It combines the selected weights you enter. A full weighted-overlap calculation requires complete, consistently dated holdings lists and an explicit matching method.
Do similar holdings guarantee similar future returns?
No. Different weights and additional holdings can change results. Neither fund guarantees capital or a predictable return, and neither completes a global multi-asset portfolio.
Sources and research notes
Provider descriptions were reviewed October 5, 2026. Numerical examples, fictional companies and calculator defaults were created for this guide; no illustrated weight is presented as live holdings data. For a broader selection framework, see researching an ETF and building an ETF portfolio.
- Vanguard: VOO fund documents and holdings
- Vanguard: VTI fund documents and holdings
- Vanguard: benchmark and fund name changes
- S&P Dow Jones Indices: S&P 500
Educational content, not personalized investment advice. Investing involves risk, including loss of principal. Illustrations are conceptual; calculations exclude taxes and trading costs.
