Five Funds, One Bet: Finding the Duplication Hiding in Your Portfolio

ETF overlap is how much two or more of your ETFs own the same stocks. To check it, compare the funds’ full holdings lists, add up the weight they share, and then work out your real exposure to the largest companies across your whole portfolio.

That last step is where most investors get a surprise. You can own five different ETFs with five different names and still be making mostly the same bet, several times over.

This guide shows you how to check overlap step by step, how to read the result, and what to do about it. It sits within FRC’s complete step-by-step guide to investing in ETFs, which walks through every stage from opening an account to building a portfolio.

Five Funds, One Bet: Finding the Duplication Hiding in Your Portfolio

Overlap happens because so many popular exchange-traded funds are built from the same pool of companies. A US large-cap fund, a US total market fund, a growth fund, a technology fund and an S&P 500 fund all draw heavily on the same biggest names.

Most of these funds are weighted by market value. That means the largest companies take the largest share of each fund, so the same handful of stocks sit at the top of one fund after another.

Owning more funds feels like more diversification. But diversification comes from owning different things, not more things. Five funds that share their top holdings can leave you less diversified than one well-chosen fund, which is why FRC’s guide to how many ETFs you should own starts with what each fund adds, not how many you hold.

If you are building your knowledge from the ground up, FRC’s ETF Investing for Beginners course covers how ETFs are built and what you actually own. ETF Investing Strategies and Advanced ETF Investing go further into portfolio construction, concentration and risk. FRC’s programmes and memberships are open to everyone.

What Overlap Looks Like in Real Portfolios

The most common overlap is between an S&P 500 fund and a total US stock market fund. The S&P 500 makes up the large majority of the US market’s total value, so a total market fund is, by weight, mostly the S&P 500 plus a long tail of smaller companies.

Hold VOO and VTI together and you are buying the same large companies twice, with a small slice of mid and small companies added. FRC’s comparison of VOO vs VTI vs QQQ walks through how these three popular funds relate.

The second common pairing is an S&P 500 fund with a Nasdaq-100 fund such as QQQ. Most of the Nasdaq-100’s companies are also in the S&P 500, and the largest technology companies sit near the top of both. Adding QQQ to VOO does not add many new companies. It mainly increases your weight in the ones you already own.

The third is the “one of each” portfolio: an S&P 500 fund, a growth fund, a technology fund and a dividend fund. The growth and technology funds tend to share the same top holdings as the S&P 500 fund, while the dividend fund may overlap less, but with a different set of familiar names.

Overlap also happens across accounts. A target-date fund in your 401(k) already holds a broad US stock fund. Add an S&P 500 ETF in your IRA and a total market ETF in your brokerage account, and the same companies appear three times without any single account looking unusual.

The Funds That Are Almost Identical

Some overlap is close to total. VOO, IVV and SPY all track the S&P 500, so their holdings are essentially the same companies in essentially the same weights. Owning two or three of them adds nothing except extra line items on your statement.

The same is true across providers for other indexes. Two total US market funds from different companies, or two Nasdaq-100 funds such as QQQ and QQQM, give you near-identical exposure. The differences that matter between them are cost, structure and trading features, not what they hold.

Investors often end up with these pairs by accident, perhaps after moving accounts between brokerages or following different recommendations at different times. They are the easiest overlap to fix, because consolidating into one fund changes your costs and paperwork while leaving your actual exposure the same.

Overlap Inside All-in-One Funds

Target-date funds and balanced funds are portfolios in a single ticker. A typical target-date fund holds a total US stock fund, an international stock fund and one or more bond funds, in proportions that shift as the target year approaches.

That makes them easy to overlap with. Add an S&P 500 ETF alongside a target-date fund and you are tilting further towards US large companies than the fund’s designers intended, and changing the very allocation you chose the fund for.

If you hold an all-in-one fund, check its underlying funds first. They are listed in the fund’s documents, and they tell you exactly which exposures you already have before you add anything else.

Checking Overlap With Mutual Funds and 401(k) Funds

The same method works for mutual funds. Many investors hold a mutual fund in a 401(k), such as an S&P 500 index fund like FXAIX, alongside an ETF such as VOO in a brokerage account. Both track the same index, so the overlap is close to total, even though one is a mutual fund and the other an ETF.

The difference is the data. ETFs usually publish their full holdings every day, while mutual funds usually publish them monthly or quarterly, often with a delay of several weeks. For an index fund that barely matters, but for an actively managed mutual fund the holdings you see may already be out of date.

Two Ways to Measure Overlap

There are two ways to measure overlap, and they tell you different things. The first is count overlap: how many companies the two funds have in common.

Count overlap can mislead. Two funds might share 80 companies, but if those companies make up a tiny share of one fund, the real overlap is small. Equally, two funds might share only 50 companies that make up most of the value of both.

The second is weight overlap, which is what matters. For each company the two funds share, you take the smaller of its two weights, then add those numbers up. The total is the percentage of the two funds that is effectively identical.

A Worked Example of Weight Overlap

Here is a simplified example with three companies. In Fund A, Company 1 is 7% of the fund, Company 2 is 6% and Company 3 is 5%. In Fund B, the same three companies are 9%, 8% and 2%.

For each company, take the smaller weight. That gives 7% for Company 1, 6% for Company 2 and 2% for Company 3. Add them up and these three companies alone create 15% of weight overlap between the two funds.

Repeat that across every shared holding and you have the full weight overlap. A result under 20% means the funds are largely different. A result above 50% means they are mostly doing the same job, and above 80% you own two versions of essentially the same portfolio, usually at two different prices.

Why Overlap Tools Show Different Numbers

If you check the same two funds in two different tools, you may get two very different answers. That is usually because the tools are measuring different things.

Weight overlap, the method above, gives one number for the pair. Some tools instead report one-way overlap: what share of Fund A’s holdings also appear in Fund B. That figure changes depending on which fund you start from.

Take QQQ and VOO. Most of QQQ’s companies are also in VOO, so measured from QQQ’s side the overlap looks very high. Measured from VOO’s side it looks much lower, because QQQ holds only around 100 of VOO’s roughly 500 companies.

Both numbers are correct. Check which one a tool is showing before you act on it.

How to Check ETF Overlap, Step by Step

Step one is to list every fund you own, in every account. Include your 401(k), IRAs, brokerage accounts and any target-date or balanced funds, because those hold stock funds inside them.

Step two is to get the full holdings of each fund. Fund providers publish complete holdings lists on each fund’s own page, usually updated daily for ETFs, and most let you download them as a spreadsheet. The fact sheet shows only the top 10, which is a useful first look but not enough for an accurate check.

Step three is to compare the funds. Many brokerages offer portfolio analysis tools that show overlap and sector exposure across your accounts, and free online overlap tools let you enter two tickers and see their shared holdings and weight overlap. If you prefer to do it yourself, put both holdings lists in one spreadsheet and match the tickers.

Step four is to look through to your real exposure. This is the step that turns overlap from an abstract percentage into a number you can act on.

Find Your Real Exposure to a Single Stock

Your real exposure to a company is the sum of what you hold through every fund. For each fund, multiply your share of the portfolio in that fund by the company’s weight inside the fund, then add the results.

Take a $100,000 portfolio split $50,000 in an S&P 500 fund, $30,000 in a Nasdaq-100 fund and $20,000 in a technology sector fund. Suppose one large company is 7% of the S&P 500 fund, 9% of the Nasdaq-100 fund and 15% of the technology fund.

Your exposure is $3,500 plus $2,700 plus $3,000, or $9,200. That is 9.2% of your whole portfolio in a single company, more than its weight in any broad index fund, even though you never bought the stock directly.

Do the same for the top five or ten names and you may find that a large share of your money rides on a small group of companies. That is concentration, and overlap is how it builds without you noticing.

Pairwise Checks vs Whole-Portfolio Checks

Most free overlap calculators compare two funds at a time. That is useful for deciding whether to add a new fund, but it can miss the bigger picture when you own three, four or more.

A whole-portfolio check, often called an X-ray, merges every fund and every stock you own into one view. It shows your combined weight in each company, each sector and each country, based on how much money you actually hold in each fund.

When choosing a tool, look for four things: it compares more than two funds at once, it lets you enter the dollar amount in each fund, it shows sector and country breakdowns, and it lets you add individual stocks you hold directly. Many brokerages build this into their portfolio analysis pages, and several free tools online do the same.

Do not forget stocks you own outright. If you hold shares in a large company directly and also own it through three index funds, your real exposure is the direct holding plus everything that comes through the funds.

The Quick Top-10 Estimate

If you want a fast check before doing the full calculation, start with each fund’s fact sheet. It lists the top 10 holdings and what share of the fund they make up.

Multiply that share by how much of your portfolio sits in the fund. If an S&P 500 fund holds a third of its value in its top 10 companies and makes up 60% of your portfolio, about 20% of your money rides on those 10 names through that fund alone.

Add the same estimate for your other stock funds, especially growth and technology funds, which usually hold the same names at even higher weights. If the total is well above what a single broad index fund would give you, it is worth running the full check.

Check Sector and Style Overlap Too

Overlap is not only about individual stocks. Two funds can hold different companies and still pile you into the same sector or the same investment style.

A technology fund and a growth fund may share many holdings, but even where they differ, both lean heavily towards technology and communication companies. Add an S&P 500 fund, where technology is already the largest sector, and your sector weight can end up far above the market’s.

Most brokerage analysis tools show your combined sector breakdown. Compare it with a broad market fund. If one sector is far heavier in your portfolio than in the market, you have made a sector bet, whether you meant to or not.

Style overlap works the same way. A large-cap growth fund and a technology fund may share only some of their holdings, but both lean towards fast-growing, highly valued companies. When that style falls out of favor, they tend to fall together, so check whether your funds share the same tilt towards growth, value, company size or dividends.

Overlap in Bond ETFs

Bond funds overlap too, but you check them differently. Broad US bond ETFs such as BND and AGG track very similar indexes of government, corporate and mortgage bonds, so holding both adds little.

Comparing individual bonds is rarely useful, because a broad bond fund can hold thousands of them. Instead, compare the funds’ mix of issuers, credit quality and duration, which measures how sensitive the fund is to interest rate changes. Two bond funds with the same mix and similar duration will behave in much the same way, whatever their individual holdings.

How Much Overlap Is Too Much?

There is no single correct number, because some overlap is deliberate. What matters is whether you chose it.

A useful rule of thumb: below about 20% weight overlap, the funds are doing different jobs. Between about 20% and 50%, there is meaningful duplication, so check that the second fund is adding a tilt you actually want, such as more technology or more small companies. Above about 50%, the funds are mostly doing the same job, and above 80% you are paying two expense ratios for nearly identical exposure.

The pairings investors ask about most give a sense of scale. S&P 500 funds such as VOO and SPY overlap almost completely. An S&P 500 fund and a Nasdaq-100 fund such as QQQ typically come out at around half by weight, though the exact figure shifts as index weights change, so check the current number in an overlap tool.

Deliberate overlap is fine. A core S&P 500 fund plus a smaller technology fund is a conscious decision to own more technology than the market does, and it is exactly how a core and satellite ETF portfolio is designed to work. The problem is accidental overlap: owning several funds because each one looked good on its own, without checking what they add up to together.

When Overlap Is Not a Problem

Some combinations look like overlap but are not. A US total market fund and an international fund such as VXUS hold almost nothing in common, so together they cover most of the world’s listed companies with very little duplication.

A stock fund and a bond fund do not overlap at all. Their job is to behave differently, and the correlation between them, how closely their prices move together, matters more than their holdings.

Even two dividend funds can have modest overlap. Funds that screen for dividend growth, high yield or dividend quality often pick quite different companies, which is why FRC’s guide to SCHD for passive income looks closely at how its screening rules shape what it holds.

How to Fix Too Much Overlap

Start by deciding what each fund is for. Every fund in a portfolio should have a job: broad US exposure, international exposure, bonds, or a deliberate tilt. If two funds are doing the same job, you only need one.

Then simplify. For most investors, one broad US fund, one international fund and one bond fund cover the core, the structure behind the three-fund portfolio, and anything else is a choice to tilt. Keeping the core in one fund per job is the quickest way to cut overlap and make your asset allocation easy to see.

Be careful about tax. Selling in a taxable brokerage account can trigger capital gains tax. It is often better to fix overlap gradually: direct new money into the funds you want to keep, use dividends the same way, and make larger changes inside IRAs and 401(k)s, where trades do not create a tax bill. FRC’s guide to where to hold ETFs explains how each account type is taxed.

Finally, keep checking. Index weights shift as companies grow and shrink, so overlap and concentration change over time even if you never trade. A quick review once a year, alongside your regular check on how to rebalance an ETF portfolio, keeps the picture clear.

Overlap Outside the United States

Overlap works the same way wherever you invest. Investors in Europe, the UK, the Middle East and Asia often buy UCITS ETFs, many of them domiciled in Ireland, that track the same indexes as US-listed funds.

An S&P 500 UCITS ETF holds the same companies as VOO or SPY, so pairing it with a world fund or a US technology fund creates exactly the overlap described in this guide. A global fund tracking developed markets already holds a large share of its value in US companies, so adding a separate US fund on top raises your US weight further.

The method is identical: download the holdings, measure weight overlap, and look through to your real exposure. Several free overlap tools now cover UCITS funds as well as US-listed ETFs.

Overlap and Cost

Overlap has a hidden cost. If two funds hold mostly the same companies, you may be paying a higher fee on the second fund for exposure you already had at a lower price.

Suppose you hold an S&P 500 fund charging 0.03% and a large-cap growth fund charging 0.40%, with heavy overlap between them. Much of what you pay 0.40% for is exposure the cheaper fund already gives you. On $50,000 in the growth fund, that is $200 a year, much of it spent duplicating what you already own.

That is why checking overlap and checking costs belong together. FRC’s Fidelity index funds comparison is a good example: four funds from one provider, with substantial overlap and very different structures, where the details decide which one makes sense.

Overlap Is a Concentration Question

The real reason to check overlap is concentration. When the same companies appear across all your funds, your portfolio’s result increasingly depends on how those few companies perform.

That can work brilliantly when those companies lead the market. It can hurt when they fall together, because the funds you thought were diversified all drop at the same time. Overlap does not change the risk of any single fund. It changes the risk of the whole portfolio.

Checking overlap does not tell you what to buy. It tells you what you already own. What to buy is a decision only you, or a licensed professional who knows your full situation, can make, and FRC’s step-by-step guide on how to choose an ETF walks through the factors that matter.

Common Questions

What is ETF overlap? ETF overlap is the share of two or more ETFs that is invested in the same companies. It is best measured by weight, not by the number of shared holdings.

How do I check if my ETFs overlap? Download each fund’s full holdings from the fund provider, then compare them in a spreadsheet, a brokerage portfolio analysis tool or a free online overlap tool. Look at weight overlap and your combined exposure to the largest companies.

Is it bad to own VOO and VTI together? It is not harmful, but it is mostly duplication. The large companies in VOO make up most of VTI by weight, so owning both adds little beyond a small amount of extra mid and small company exposure.

Do VOO and QQQ overlap? Yes. Most Nasdaq-100 companies are also in the S&P 500, and the largest technology companies sit near the top of both, so adding QQQ to VOO mainly increases your weight in companies you already own.

How much should ETFs overlap? As a rule of thumb, under about 20% weight overlap means the funds add distinct exposure, 20% to 50% is meaningful duplication worth checking, and above 50% the funds are mostly doing the same job. Overlap is fine when it is a deliberate tilt you have chosen.

What is the best tool to compare ETF overlap? The most useful tools compare several funds at once, let you enter how much you hold in each, include individual stocks and show sector and country exposure. Many brokerages offer this in their portfolio analysis pages, and free online overlap tools cover both US-listed and UCITS ETFs.

Build Portfolios You Actually Understand

Overlap is one of the simplest checks in investing and one of the most skipped. It takes an hour, a few holdings files and a spreadsheet, and it shows you what your portfolio really is rather than what the fund names suggest.

That habit, looking through the labels to what you own, is what separates confident investors from hopeful ones. FRC’s three ETF courses build it step by step, from how a fund is constructed to how a full portfolio fits together, and the FRC dictionary explains every term along the way, free for everyone.

Know what you own. Know why you own it. Then every fund in your portfolio earns its place.