Hold VOO and QQQ together and you might think you've built something diversified. Two big ETFs, two different indexes, the S&P 500 on one side, the Nasdaq-100 on the other.

Run the actual numbers and 95.6% of QQQ is already inside VOO.

That sentence does a lot of work in this article, so I'll come back to it. The point of the intro is that most investors never check. They buy the second ETF because someone on Reddit said it adds tech exposure, or because a YouTube model portfolio includes both. They assume two tickers means two distinct bets. The holdings overlap question, the one that decides whether you actually diversified or just bought 105% of Apple and 110% of Nvidia, never gets asked.

It can be answered for free in about thirty seconds. The Awalyt ETF overlap analyzer pulls full holdings for two funds, calculates the weighted overlap, shows you the top shared positions, and breaks down how the sector mix differs. This article walks through how to use it, what the VOO vs. QQQ numbers actually look like, why this matters more than it sounds, and where the limits of a single overlap check are. Being clear about what the tool can't tell you is part of being useful.

Disclaimer: This article is for educational and informational purposes only. It does not constitute investment advice. Past performance does not guarantee future results. Always do your own research before making any investment decisions.

How to Run the Check in 30 Seconds

Open the Awalyt ETF overlap analyzer. Free, no signup, no email required.

Two inputs:

Awalyt ETF overlap analyzer input form with two ticker fields and an Analyze overlap button

First ETF and Second ETF. Type the two tickers you want to compare. The search autocompletes from the supported universe. You can compare any two US-listed ETFs the tool has holdings data for. Common pairs people check: VOO vs. QQQ, VTI vs. VOO, VOO vs. SCHD, VTI vs. VXUS.

Click Analyze overlap and the tool returns five things.

What the Tool Shows You

A verdict. A quick qualitative label, Very High / High / Moderate / Low overlap, so you have an immediate read before you scan the numbers.

Weighted overlap percentage. The sum, across all shared holdings, of the smaller weight in each fund. This is the right way to measure overlap, because it counts the dollar amount actually duplicated when you hold both. A holding that's 8% of VOO and 9% of QQQ contributes 8% (the smaller side) to the overlap, because that's how much you actually double up if you own both ETFs equally.

Overlapping holdings count and coverage asymmetry. How many tickers are in both funds, and what fraction of each fund's portfolio sits inside the other. The asymmetry matters: a small narrow ETF can be almost fully contained inside a large broad one, while the broad one only has a fraction of itself overlapping with the narrow.

Top overlapping holdings table. The 10 largest shared positions, with each ETF's individual weight and the overlap contribution side by side.

Sector allocation comparison. A side-by-side bar chart of how each ETF distributes across the 11 GICS sectors. Even when the holdings overlap heavily, the sector tilt can differ in revealing ways.

About thirty seconds of input, a complete portfolio-composition read on the other side.

The Example: VOO vs. QQQ in Real Numbers

This is the comparison most US DIY investors should run at least once. Here's what the tool returns.

ETF overlap analyzer result for VOO vs QQQ showing Very High Overlap verdict, 53.12% weighted overlap, 89 overlapping holdings, and coverage asymmetry of 53.9% VOO inside QQQ versus 95.6% QQQ inside VOO

The verdict is Very High Overlap. The weighted overlap is 53.12%. There are 89 overlapping holdings, out of 500 in VOO and 102 in QQQ.

The coverage asymmetry is the most underrated number on the page. 53.9% of VOO sits inside QQQ. 95.6% of QQQ sits inside VOO. If you hold both equally, you haven't added a second strategy to your portfolio. You've added a near-subset of the first strategy with a small amount of unique exposure on top. Almost all of QQQ is already what VOO does.

Then there's the top-10 shared positions, sorted by overlap contribution:

Top 10 overlapping holdings between VOO and QQQ showing NVDA, AAPL, MSFT, AMZN, AVGO, GOOGL, META, GOOG, TSLA, NFLX with weights in each ETF and contribution to overlap

NVDA, AAPL, MSFT, AMZN, AVGO, GOOGL, META, GOOG, TSLA, NFLX. The familiar mega-cap tech cohort, weighing roughly 8-9% in VOO and 9-10% in QQQ each at the top of the list. If you hold a 50/50 VOO + QQQ split, you're not "diversifying across two indexes". You're holding Nvidia at something like 9% of your portfolio, Apple at 8%, Microsoft at 7%, and so on. The first six positions alone account for more than 30% of your money.

And the sector breakdown makes the structural difference visible:

Sector allocation comparison between VOO and QQQ across all 11 GICS sectors, showing QQQ heavily concentrated in Information Technology and Communication Services with zero exposure to Financials and minimal Energy, while VOO has more balanced sector spread

QQQ is roughly 55% Information Technology against VOO's 35%. QQQ has near-zero Financials and Energy, while VOO carries meaningful exposure to both. Communication Services tilts QQQ-heavy too. The "extra" you get from holding QQQ on top of VOO isn't broad diversification, it's a concentrated overweight in IT and Communications and an explicit underweight in Financials and Energy.

A 50/50 VOO + QQQ portfolio is not wrong. It's a real allocation choice with real tradeoffs. But it's an active bet on continued mega-cap tech outperformance, not a diversified S&P-plus-Nasdaq strategy. The two framings sound similar and lead to very different conversations with yourself when 2022 happens again.

Why It Matters

A few reasons why the thirty-second check is worth doing before, not after.

What You Own ≠ What the Fund Names Suggest

Fund names are marketing. "S&P 500" and "Nasdaq-100" sound like two different exposures because the indexes have different names and rules. Under the hood they share most of the same companies, weighted slightly differently. The same pattern repeats with VTI vs. VOO ("total market" vs. "large cap" sound distinct, but more than 80% of VTI by weight is essentially VOO), and with VOO vs. SCHD ("growth" vs. "dividend" sound opposite, but the overlap in mega-cap names is non-trivial).

If your mental model of your portfolio is built from the fund names, it's probably overestimating how diversified you actually are.

Concentration Without Intent Is the Most Common DIY Mistake

It's fine to be concentrated in mega-cap US tech. It's a defensible thesis, and a lot of people who hold it explicitly have done well for the last decade. What's not fine is being that concentrated without realizing it, because that's a risk profile you didn't actually choose. When the next significant tech drawdown happens, the investor who chose the tilt knows what they signed up for. The investor who thought they were diversified across two indexes gets a different lesson.

The overlap analyzer doesn't tell you whether your concentration is good or bad. It tells you whether it's intentional.

This Is What Most "Diversified" DIY Portfolios Actually Look Like

A common Bogleheads-style 4-fund portfolio: VTI, VXUS, BND, maybe a tilt like SCHD or VYM. Run the overlap check across the US-equity sleeve. VTI vs. VOO is heavily overlapped. VTI vs. SCHD shares the dividend payers in the large-cap space. The diversification you actually have is mostly across asset classes (US equity vs. international equity vs. bonds), not across funds within an asset class.

This isn't a problem, it's a clarification. The diversification benefit comes from holding bonds and international, not from holding two different US large-cap ETFs.

Correlation Tells You After. Overlap Tells You Before.

If you run a portfolio backtest on Awalyt's correlation matrix you'll see VOO and QQQ correlating around 0.85-0.90 daily. That's how the two funds behaved together historically. Correlation is a post-hoc measurement, useful for understanding what happened.

Overlap is the structural reason behind the correlation, and you can see it before you buy. ETFs that share most of their holdings will move together. The high correlation isn't a coincidence or a market quirk. It's arithmetic, baked into the composition, and visible from a thirty-second check.

The Honest Limits

A few things the analyzer doesn't do, worth being explicit about.

It's a composition snapshot, not a forecast. The tool tells you what's inside the two funds today. It doesn't tell you how the overlap will behave in the next decade, or whether holding both is the right call for your situation.

Holdings data is refreshed periodically, not real-time. Between an ETF's internal rebalancing and the data refresh, there's a small lag. For stable funds like VOO or QQQ with low turnover this is irrelevant. For high-turnover or actively managed funds, treat the overlap number as accurate within a small margin rather than exact to the basis point.

The verdict labels are a quick reference, not a hard rule. "Very High Overlap" at 53% means the funds share most of their weight, but whether that's a problem for your portfolio depends on the rest of what you hold and why you're holding it. A 53% overlap inside a tech-tilted satellite allocation is intentional. The same 53% inside what you thought was a "diversified core" is a flag.

Two ETFs at a time is a starting point. Most DIY portfolios hold four or five funds, and pairwise overlap doesn't compose into a clean portfolio-level concentration picture. To see total holding concentration across a full multi-ETF portfolio, you need a portfolio-level view, not pairwise checks.

The tool shows you the structure. The decision is still yours. Knowing that QQQ is 95.6% inside VOO doesn't tell you whether to sell QQQ, double down, or hold both intentionally. That depends on context the tool can't see: your time horizon, your other positions, your risk tolerance, your tax situation. The overlap analyzer improves the quality of the decision. It doesn't make the decision.

What to Try First

Four overlap checks that build intuition fast. Each takes under a minute.

VOO vs. QQQ. The case in this article. Run it once if you've never seen the numbers; it changes how you read every other ETF recommendation that pairs the two.

VOO vs. VTI. "S&P 500" vs. "Total Market". The overlap is very high, because VTI is mostly the same large-caps plus a small-cap and mid-cap tail. This shows you that the "I want broader market exposure" intuition is largely already satisfied by VOO alone.

VOO vs. SCHD. The "growth vs. dividend" pairing a lot of US investors hold. The overlap is meaningful in the mega-cap dividend payers. SCHD adds dividend yield and lower tech weight, but it's not as orthogonal to VOO as the naming implies.

VTI vs. VXUS. A sanity check on the tool and on yourself. If you've built a portfolio with these two as the core, you should see ~0% overlap (US total market vs. international ex-US). Confirming that visually makes the framework click: this is what genuine diversification looks like, and it's the exception, not the rule, among popular ETF pairs.

If you want the companion piece on the DCA side of free Awalyt tools, the DCA calculator guide covers the same logic for testing a contribution strategy before committing to it.

Beyond Two ETFs: Where Portfolio-Level Analysis Lives

The overlap analyzer answers the pairwise question. Most real portfolios eventually have a multi-fund question that pairwise checks can't fully answer.

If you hold VTI, VXUS, BND, SCHD, and a tech tilt, the total mega-cap concentration across the US-equity sleeve, the correlation structure across all five positions, and how the portfolio would have behaved through past drawdowns are portfolio-level questions, not pairwise ones. That's what the broader Awalyt platform is built for: full-portfolio analysis on the same holdings and price data the free tools use, with correlation matrices, drawdown analysis, and the daily-precision backtesting engine extended to multi-asset rebalancing.

For more on what serious portfolio backtesting includes and why daily data matters there, the introduction to portfolio backtesting is the place to start.

Bottom Line

Holding VOO and QQQ together can be a perfectly reasonable allocation choice. Holding them together without knowing that 95.6% of one is already inside the other isn't a choice, it's an accident.

The fix takes thirty seconds and costs nothing. The analyzer is here the next time you're considering adding a second ETF to something you already hold.

This article is for educational and informational purposes only. It does not constitute financial, investment, or tax advice. Past performance does not guarantee future results. Always do your own research and consider consulting a qualified financial advisor before making investment decisions.

How to Check ETF Overlap for Free — And Why You Should Before Buying Two ETFs [2026]