Fund overlap is the share of two portfolios invested in the same securities. To measure it, take the smaller of the two funds' weights for every company both hold and add those minimums; the total is the weighted overlap percentage. To read it, check two things the single number hides: whether the tool weighted by position size or only counted names (on QQQ and SPY the two methods differ by 37.6 points), and which fund is the subset (98.8 percent of VOO's weight sits in companies VTI also holds, while only 86.8 percent of VTI's weight sits in VOO's companies).
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This guide covers the three methods behind the number, measured figures for nineteen ETF and mutual fund pairs, and a repeatable way to look at a whole portfolio rather than one pair at a time. For a broader side-by-side ETF comparison (cost, returns, sectors, risk), see how to compare ETFs.
Data and method used in this article
Every figure in this article was computed on August 18, 2026 from each fund's most recently published holdings weights as retrieved on that date, supplied through the MarketXLS fund data platform. Market data is provided by QuoteMedia. Funds publish holdings on their own schedules, so the two files compared in any one pair can carry different publication dates, and that point matters for one of the results below. The calculation is the minimum weight method defined further down.
All figures are derived estimates rather than official fund disclosures, and they will differ at other dates. Where an older MarketXLS article quotes a rounded figure for one of these pairs, the number below supersedes it, because these were recomputed on a single date with a single stated method.
Fund overlap across thirteen ETF pairs
Read the column as the share of two portfolios that is genuinely the same money in the same companies.
| Fund pair | Weighted overlap | What is going on |
|---|---|---|
| SPY and VOO | 94.5% | Same index, two wrappers |
| VOO and VTI | 86.8% | The S&P 500 sits inside the total market |
| QQQ and VUG | 62.7% | Different indexes, same mega cap growth names |
| VOO and VUG | 57.5% | Growth is a subset of the blend |
| QQQ and SPY | 54.4% | The largest Nasdaq names are also the largest S&P names |
| VTI and VUG | 51.6% | Total market already contains the growth sleeve |
| VOO and VGT | 37.9% | Sector fund concentrated inside the broad index |
| SPY and DIA | 29.2% | Thirty large caps, all present in the 500 |
| SCHD and VYM | 20.8% | Two dividend screens, different construction |
| VOO and SCHD | 7.6% | Dividend screen tilts away from the index leaders |
| VTV and VUG | 3.6% | Value and growth split the same parent index |
| VOO and IWM | 0.1% | Large cap and small cap barely intersect |
| VOO and VXUS | 0.1% | Domestic and international are genuinely separate |
Two things stand out. The pairs most investors worry about, such as value against growth or domestic against international, are already clean. The pairs that produce real duplication are the ones that look different on the label, such as QQQ against VUG at 62.7 percent, where one fund tracks the Nasdaq 100 and the other tracks a broad growth index, and they still land on the same eight companies.
How the minimum weight method works
For every company held by both funds, take the smaller of the two portfolio weights, then add those minimums across all shared companies. If Fund A puts 6 percent in a company and Fund B puts 4 percent in the same company, the overlap contribution is 4 percent, because only 4 points of that position are genuinely duplicated. The remaining 2 points in Fund A are exposure Fund B does not provide.
That method answers a specific question: if you hold equal amounts of both funds, how much of the combined portfolio is redundant.
Three ways the number gets calculated
When two calculators disagree about the same pair, it is almost always because they answered different questions.
Method one, shared holdings by name. Count the companies appearing in both funds, then divide by the size of the combined list. This ignores weight entirely, so a position that is 0.01 percent of a fund counts as much as one that is 8 percent.
Method two, weighted overlap by minimum weight. The method described above. It respects position size, so it tracks what a portfolio actually experiences.
Method three, directional weight share. For each fund separately, add the weight sitting in companies the other fund also holds. This produces two numbers instead of one, and it is the most informative of the three.
The gap between method one and method two is not academic. On the same pairs, computed on the same day:
| Pair | Weighted overlap | Shared holdings by name | Gap |
|---|---|---|---|
| QQQ and SPY | 54.4% | 16.8% | 37.6 points |
| QQQ and VUG | 62.7% | 29.8% | 32.9 points |
| VOO and VGT | 37.9% | 10.7% | 27.2 points |
| SPY and DIA | 29.2% | 6.0% | 23.2 points |
| SCHD and VYM | 20.8% | 12.8% | 8.0 points |
QQQ and SPY is the clearest case. Counted by name, only 16.8 percent of the combined roster is shared, because SPY holds around 500 companies and QQQ holds around 100, so the combined list is dominated by names only SPY holds. Weighted by position size, 54.4 percent of the money is in the same companies. The first number describes the rosters. The second describes the portfolio. Check which method a tool uses before comparing its output to another tool's.
The direction problem: one number, two answers
A single overlap percentage is symmetric. Real duplication usually is not.
Take VOO against VTI. The weighted overlap is 86.8 percent. Split it by direction and the picture changes:
- 98.8 percent of VOO's weight sits in companies VTI also holds.
- 86.8 percent of VTI's weight sits in companies VOO also holds.
VOO is almost entirely contained inside VTI. VTI holds a meaningful amount that VOO does not, mostly mid and small cap companies. The relationship is a subset relationship rather than a mutual one, and only the directional split reveals that.
The asymmetry gets more pronounced as the funds diverge in size:
| Pair | Weighted overlap | Share of fund A weight in shared names | Share of fund B weight in shared names |
|---|---|---|---|
| QQQ and SPY | 54.4% | QQQ 94.6% | SPY 54.4% |
| SPY and DIA | 29.2% | SPY 38.9% | DIA 99.9% |
| VTI and VUG | 51.6% | VTI 51.9% | VUG 98.8% |
| SCHD and VYM | 20.8% | SCHD 96.4% | VYM 20.8% |
| VOO and VGT | 37.9% | VOO 37.9% | VGT 86.9% |
SPY and DIA report a modest 29.2 percent overlap, which sounds comfortable. Look at the direction and 99.9 percent of DIA's weight is in companies SPY also holds. DIA introduces almost no companies that SPY does not already hold. What it does introduce is a different weighting scheme, which is a distinct property from holding different companies.
SCHD and VYM show the same shape. The symmetric figure is 20.8 percent, yet 96.4 percent of SCHD's weight is in companies VYM also holds, while only 20.8 percent of VYM's weight is in companies SCHD holds. The relationship runs strongly in one direction.
The habit worth building is simple. Never read the symmetric number on its own. Ask which fund is the subset.
Why near identical funds do not measure at 99 percent
The first table reports SPY and VOO at 94.5 percent, rather than the near 100 percent that two funds tracking one index might suggest. The reason is a property of the data, not of the funds.
An overlap calculation compares two published holdings files. Each fund publishes on its own schedule, so the two files being compared are rarely snapshots of the same moment, and the weights they carry for the same company differ slightly as a result. Because the minimum weight method takes the smaller weight on every line, each of those small differences subtracts from the total, and across several hundred positions the effect accumulates.
The pattern holds across every near identical pair measured:
| Pair | Weighted overlap | Relationship |
|---|---|---|
| SPY and VOO | 94.5% | Two ETFs tracking the same index |
| VFIAX and FXAIX | 93.8% | Two mutual funds, same index, different providers |
| VFIAX and SWPPX | 91.0% | Two mutual funds, same index, different providers |
| FXAIX and SWPPX | 90.4% | Two mutual funds, same index, different providers |
None of these measures above 95 percent, although all four pairs are, economically, close to the same portfolio in different containers. The practical rule that follows is to read anything in the low 90s or above as effectively the same portfolio, rather than waiting for a figure that published holdings data will rarely produce.
Mutual funds: what changes and what does not
The calculation is identical for mutual funds. The data behind it is not.
Most ETFs publish holdings daily. Many mutual funds disclose holdings quarterly, with a reporting lag. An overlap figure involving a mutual fund is therefore computed against the most recent disclosure rather than against today's portfolio. For index funds this matters little, because the portfolio moves slowly, which is why the index fund pairs above cluster so tightly. For an actively managed fund with meaningful turnover, a figure based on a quarter old disclosure is an estimate and should be treated as one.
The mutual fund figures also make a point that a pure ETF table cannot. Overlap does not respect the wrapper. Several large index funds are offered both as a mutual fund share class and as an ETF share class of one underlying portfolio, so a workplace plan index fund and a brokerage ETF can be nearly the same holding while appearing on separate statements under different tickers.
Two practical consequences follow. Read the disclosure date alongside the percentage. Re-run the check after an actively managed fund's next disclosure.
Where the overlap actually comes from
Overlap percentages are dominated by a handful of positions. On the QQQ and VUG pair, the 62.7 percent total breaks down like this:
| Company | Overlap contribution |
|---|---|
| NVDA | 8.44% |
| AAPL | 7.27% |
| MSFT | 5.76% |
| AMZN | 4.46% |
| GOOGL | 3.36% |
| AVGO | 3.16% |
| GOOG | 3.13% |
| META | 2.78% |
Eight positions account for 38.4 of the 62.7 points, so roughly 61 percent of all duplication between these two funds traces to eight companies. Around fifty other shared companies contribute the rest.
That distinction matters. If overlap were spread evenly across hundreds of positions, the finding would simply be that two funds are similar. When it concentrates this way, the more accurate description is that a portfolio carries a large single company exposure arriving through two different funds. Those are different observations about the same number.
A look-through view of a four fund portfolio
Pairwise overlap is where most analysis stops, and it is not enough. Consider a portfolio holding VOO, QQQ, VUG and SCHD in equal quarters. The pairwise grid:
| Pair | Weighted overlap |
|---|---|
| VOO and QQQ | 54.5% |
| VOO and VUG | 57.5% |
| VOO and SCHD | 7.6% |
| QQQ and VUG | 62.7% |
| QQQ and SCHD | 5.0% |
| VUG and SCHD | 0.8% |
Three of the six pairs sit above 50 percent, and SCHD is measurably different from the other three. But no pairwise number describes what the combined portfolio holds. Blend the four funds at 25 percent each and look through to the underlying companies:
| Company | Weight in the blended portfolio |
|---|---|
| NVDA | 7.14% |
| AAPL | 6.38% |
| MSFT | 4.41% |
| AMZN | 3.19% |
| GOOGL | 3.09% |
| GOOG | 2.56% |
| AVGO | 2.55% |
| META | 2.02% |
| TSLA | 1.92% |
| AMD | 1.88% |
The blended portfolio holds roughly 592 distinct companies, which reads as broad diversification. Its ten largest positions account for 35.1 percent of it. Counting the two share classes of the same parent company as one position, nine companies carry more than a third of a four fund portfolio.
No single decision produced that. It emerged from stacking four reasonable funds. A look-through view surfaces it and a pairwise view does not, which is why a portfolio level pass belongs alongside the pair check.
Reading the number against the job each fund does
There is no universal threshold at which overlap becomes a problem, because a percentage only carries meaning once you know why each fund is held. A workable frame:
Funds held for the same job. Two core equity positions, or two dividend funds, or two growth funds. Overlap above roughly 70 percent here means two expense ratios are being paid for something close to a single exposure. This 70 percent line is a common rule of thumb rather than an industry standard, and different sources place it anywhere from 50 to 80 percent. It is an observation about cost and exposure, and it is not a recommendation to consolidate or to sell any fund.
Funds held for different jobs. A core holding plus a deliberate sector or factor tilt. High overlap is expected here and is not by itself a defect, because the tilt is the purpose. The question the number raises is whether the differentiated portion is large enough to change portfolio behavior.
Funds held across separate accounts. Overlap does not respect account boundaries. A workplace plan default fund and a brokerage ETF can be near duplicates, and because they appear on different statements, this version goes unnoticed longest.
Funds held for access reasons. Sometimes a near duplicate exists because a plan menu offers no alternative. The overlap is still real and still worth measuring, even when nothing about the holding changes as a result.
Five places overlap hides
- Share classes and wrappers of the same portfolio. A mutual fund and its ETF equivalent from the same provider are frequently the same portfolio in two containers.
- The subset relationship. Total market funds contain S&P 500 funds. Broad growth funds contain most large cap growth names. The container relationship is easy to miss, because the two funds carry genuinely different descriptions.
- Thematic funds landing on the same companies. Several distinct themes, such as artificial intelligence, semiconductors and cloud infrastructure, converge on an overlapping set of large companies.
- Target date and allocation funds. These hold other funds. Their look-through holdings can duplicate positions held directly, and the duplication is invisible at the ticker level.
- Portfolios assembled over time. Holdings added at different moments by different people accumulate near duplicates that nobody ever compared, because each addition was reasonable in isolation.
Running the check
You can run the whole overlap check in a browser with FundXLS, the fund and ETF research platform on MarketXLS:
- Open the ETF overlap calculator, or the mutual fund overlap calculator when the comparison involves mutual funds.
- Enter the two tickers. The result returns the weighted overlap percentage, the shared holdings, and the weight each shared company carries in both funds. A pair can also be loaded directly from a link, for example VOO against VTI or VFIAX against FXAIX.
- Read the shared holdings list before the headline number. That list shows whether the overlap is spread thin or concentrated in a few companies, which is the part that changes what the number means.
- For a side by side view of cost, holdings count and exposure, run the same pair through the fund comparison tool.
- For the look-through view described earlier, run the full set of holdings through the portfolio x-ray, which is a paid FundXLS report, rather than checking pairs one at a time.
A web tool also reads current published holdings, so the answer reflects each fund as it stands and can be repeated whenever holdings change.
What the number does not tell you
An overlap percentage measures shared securities only. Its limits:
- Overlap is a description, not a verdict. It states how much of two portfolios sits in the same securities. It does not establish whether that is appropriate for any particular portfolio, which depends on circumstances no calculator sees.
- Low overlap does not establish diversification. Two funds can hold entirely different companies in the same sector, country and size band and still move together closely. Overlap addresses one specific question only.
- High overlap does not establish redundancy. Two funds can share most of their holdings and still differ in weighting scheme, rebalancing rules, cost and tax treatment, as SPY and DIA illustrate.
- Overlap says nothing about cost, tracking difference, tax treatment, liquidity or construction. Those are separate comparisons requiring separate data.
- Every relationship changes when the portfolio changes. Adding one fund alters every pairwise figure and every look-through weight, so the check is worth repeating whenever holdings change.
Frequently asked questions
What is a good fund overlap percentage? No single threshold applies, because the answer depends on why each fund is held. As a common rule of thumb, two funds held for the same purpose with overlap above roughly 70 percent are delivering close to one exposure. Two funds held for different purposes can carry high overlap for legitimate reasons. The percentage is best read against the role each fund plays rather than against a fixed line.
Why do two overlap calculators give different answers for the same funds? Because they usually use different methods. Counting shared holdings by name produces a very different figure from weighting by position size, and on the QQQ and SPY pair those two methods differ by 37.6 points. Directional calculations produce two numbers rather than one. Check which method a tool uses before comparing outputs.
Do VOO and VTI overlap? Yes, substantially. Measured by weight on August 18, 2026, the two funds overlap 86.8 percent, and the relationship is directional: 98.8 percent of VOO's weight sits in companies VTI also holds, while 86.8 percent of VTI's weight sits in companies VOO also holds. VOO is close to a subset of VTI, and the part of VTI that VOO does not cover is mostly mid and small cap.
Does zero overlap mean two funds are properly diversified? No. Overlap measures shared securities, not shared behavior. Two funds can hold entirely different companies in the same sector, country and size band and still move closely together. Low overlap rules out one specific form of duplication. It does not by itself establish diversification.
Can I check overlap between a mutual fund and an ETF? Yes, and the calculation works the same way. The caveat is disclosure timing. ETFs generally publish holdings daily while many mutual funds disclose quarterly, so the result reflects the most recent published holdings on both sides rather than today's positions.
Why did two funds tracking the same index not measure at 100 percent? Because the calculation compares two published holdings files, and those files rarely carry identical weights or identical publication dates. Small weight differences accumulate across hundreds of positions, which is why the same index pairs in this article measure between 90 and 95 percent rather than at 99 percent.
How often should fund overlap be checked? Whenever the portfolio changes, and periodically otherwise. Adding or replacing a single fund alters every pairwise relationship, so a check at that moment carries the most information. Index funds drift slowly and an occasional review is enough, while actively managed funds are worth re-checking after each new disclosure.
The bottom line
Fund overlap is worth measuring precisely because the headline percentage is so easy to misread. The number depends on the calculation method, and two accepted methods differ by 37.6 points on the QQQ and SPY pair. It hides which of two funds is the subset. It usually traces back to a small group of companies rather than a broad similarity. Published holdings data means even near identical portfolios measure in the low 90s rather than at 99 percent. A portfolio of four sensible funds can put a third of its value into nine companies without any single decision causing it.
The useful version of this check has three parts: read the weighted number rather than a name count, split it by direction to identify the subset fund, and look through the whole portfolio rather than one pair at a time. All three run in a browser.
Start with a pair you already hold on the FundXLS platform. For a walkthrough of the fund research tools applied to a real portfolio, you can book a demo.
Related reading: fund overlap tool basics, ETF overlap and hidden duplication, and comparing mutual funds beyond past returns.
Disclaimer and disclosures
This article is educational, and it promotes MarketXLS products. It is not investment advice, tax advice, or a recommendation to buy, sell, or hold any security. MarketXLS is a software provider and is not a registered investment adviser, and nothing here is personalized advice. Consider speaking with a qualified professional about your own circumstances, including any tax consequences of a portfolio change.
All overlap figures in this article, including those in the tables and in the featured image, were computed by MarketXLS from published fund holdings weights retrieved on August 18, 2026. Market data is provided by QuoteMedia. Fund holdings and weights change over time, published holdings files carry different publication dates, and the figures will differ at other dates. These are derived estimates, and MarketXLS does not warrant their accuracy or completeness. The featured image is an illustration of the interface and does not display live results.
All fund names, ticker symbols, index names and trademarks are the property of their respective owners. MarketXLS is not affiliated with, sponsored by, or endorsed by any fund provider, index provider, or exchange named in this article. See the MarketXLS disclaimer and terms of use for further detail.