ETF Overlap Detector Calculator
Detect hidden overlap between ETFs for free by comparing top holdings side by side. Spot concentration risks in your portfolio before you invest.
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How It Works
The ETF Overlap Detector compares the top ten holdings of each ETF you own and computes pairwise overlap percentages plus an overall concentration score. Enter each fund by ticker or name, then paste comma separated holdings copied from the issuer factsheet, Morningstar, ETF.com, or Yahoo Finance. The tool deduplicates tickers within each list and compares every pair case insensitively. Example: VOO and IVV both hold Apple, Microsoft, Nvidia, Amazon, and seven other S&P 500 names, producing overlap near one hundred percent even though you hold two different tickers. Stacking QQQ on top of a broad market fund often duplicates mega cap technology weights without adding small cap or value exposure. Sector ETFs such as XLK or SMH may show moderate overlap with a core S&P fund only in the largest technology names while appearing diversified by fund title alone. International products can overlap through multinational listings when Nestle or Samsung appears in both a US listed global fund and a domestic large cap ETF.
Review the overlap matrix for each fund pair, the concentration score summary, and color coded risk bands. Below forty percent overlap suggests genuinely different sleeves. Forty to seventy percent signals partial duplication worth reviewing. Above seventy percent means you likely pay multiple expense ratios for nearly identical exposure. Run the analysis before buying a second broad market ETF, before adding a thematic fund on top of an index core, and after quarterly index rebalances when top ten weights shift. Advisors use this during onboarding to collapse redundant legacy mutual fund menus into a simpler ETF stack. After trimming duplicates, redeploy freed capital into uncorrelated sleeves such as bonds, REITs, or international ex US funds with lower pairwise overlap. Pair results with Portfolio Rebalancer to deploy cash into underweight names and Portfolio Beta to confirm risk actually fell after consolidation.
Quarterly index rebalances shift top ten weights, altering overlap scores. Advisors use this during onboarding to collapse redundant legacy mutual fund menus into a simpler ETF stack. After trimming duplicates, redeploy freed capital into uncorrelated sleeves such as bonds, REITs, or international ex US funds with lower pairwise overlap. Pair results with Portfolio Rebalancer to deploy cash into underweight names and Portfolio Beta to confirm risk actually fell after consolidation.
Use ETF Overlap Detector whenever inputs change: after market moves, new contributions, or revised personal assumptions. Bookmark the page for quick reruns without installing software.
Step by step
- Open ETF Overlap Detector and enter your current inputs.
- Review calculated outputs and summary tables.
- Adjust assumptions and compare scenarios side by side.
Worked example
The ETF Overlap Detector compares the top ten holdings of each ETF you own and computes pairwise overlap percentages plus an overall concentration score. Enter the sample inputs described in How it works to reproduce the scenario step by step.
Adjust one input at a time to see sensitivity. ETF Overlap Detector updates instantly so you can stress test optimistic and conservative assumptions before acting.
When to use this calculator
Reach for ETF Overlap Detector when detect hidden overlap between etfs by comparing their top holdings. identify concentration risks in your portfolio.. It suits quick what if analysis before trades, allocation changes, or plan updates.
Pair with related tools when the decision spans taxes, liquidity, or multi year projections beyond what one formula captures.
Common mistakes
Copying outputs without checking input units or stale market prices is a frequent error with ETF Overlap Detector. Confirm tickers, percentages, and dates before acting.
Running a single baseline scenario ignores tail risks. Stress test with conservative inputs and compare against related tools listed below when the decision is material.
The Formula
For each pair (A, B):
S_A = set of tickers in ETF A
S_B = set of tickers in ETF B
overlapPct = (|S_A ∩ S_B| / min(|S_A|, |S_B|)) × 100
Concentration Score = average of all pairwise overlapPct values
Tickers compared case insensitively. Duplicate tickers within the same ETF deduplicated. Analysis uses top ten lists not full holdings files so tail names may be missed. Concentration score equals average of all pairwise overlap percentages across your entered funds.
Limitations and assumptions
Tickers compared case insensitively. Duplicate tickers within the same ETF deduplicated. Analysis uses top ten lists not full holdings files so tail names may be missed. Concentration score equals average of all pairwise overlap percentages across your entered funds. ETF Overlap Detector does not replace personalized advice. Fees, slippage, account specific rules, and behavioral constraints may change real world outcomes.
Key terms
- Why should I care about ETF overlap
- When you own multiple ETFs that hold the same stocks, you are not as diversified as fund count suggests.
- How is overlap percentage calculated
- For each pair of ETFs A and B, the tool builds sets of tickers from each top ten list.
- Model assumption
- The concentration score is the arithmetic average of all pairwise overlap percentages.
Compare alternatives
Run Portfolio Rebalancer to redeploy overlap savings, Portfolio Beta to check risk after consolidation, ETF Expense Ratio to quantify fee stacking on duplicate funds, and Stock Chart to inspect shared mega cap names on portfolios. Use those calculators when etf overlap detector alone does not capture the full decision.
Internal links on portfolios.tools help you chain calculators: run ETF Overlap Detector first, then validate edge cases with a specialized tool from the related section below.
FAQ
Why should I care about ETF overlap?
When you own multiple ETFs that hold the same stocks, you are not as diversified as fund count suggests. The ETF Overlap Detector shows exactly which tickers repeat across funds so you can see real concentration risk. Owning VOO, IVV, and SPY together triples fees while barely adding names beyond the S&P 500. Sector tilts on top of a broad fund often duplicate mega cap technology weights without adding small cap exposure. Target date funds inside a 401k plus a taxable S&P ETF at home create hidden overlap many investors never map. Bond ETFs can overlap when both hold similar duration Treasuries. The goal is fewer funds with distinct economic exposures, not more tickers that recycle the same underlying names.
How is overlap percentage calculated?
For each pair of ETFs A and B, the tool builds sets of tickers from each top ten list. Overlap percentage equals the count of shared tickers divided by the size of the smaller set, times one hundred. One hundred percent overlap means one ETF's holdings are a complete subset of the other. Fifty percent overlap on two ten name lists means five shared tickers relative to the smaller list size. Sector ETFs may show moderate overlap with a broad fund only in mega cap technology names while tail holdings differ. International funds overlap through multinational listings such as Nestle appearing in both US and global products. The matrix is symmetric: VOO versus IVV equals IVV versus VOO.
What does the concentration score mean?
The concentration score is the arithmetic average of all pairwise overlap percentages. With three ETFs there are three pairwise comparisons. With four ETFs there are six comparisons. Adding a niche ETF that repeats half the names of your core fund raises the score even when the new fund looks different by title alone. Removing one duplicate broad market fund often drops the score more than swapping share classes between similar index products. A score of thirty with five distinct sector sleeves differs materially from thirty with two nearly identical index funds plus three satellites. Track the score over time as you rebalance or replace legacy holdings.
What is a good overlap score?
Below forty percent is low overlap: your ETFs pull different names. Forty to seventy percent is moderate: some concentration exists and fee stacking may not be justified. Above seventy percent is high: you pay multiple expense ratios for very similar exposure and should consider consolidating. Revisit overlap after rebalancing or when replacing a legacy mutual fund with ETFs. Target date funds inside a 401k plus a taxable S&P ETF at home often create hidden overlap investors never map. Zero overlap on top ten lists does not guarantee zero overlap in full holdings files, but top ten captures most weight in cap weighted index products.
Where can I find my ETF's top holdings?
Find top holdings on the issuer website under holdings or portfolio tab, on Morningstar under portfolio, on ETF.com holdings page, or Yahoo Finance under holdings. Copy ticker symbols separated by commas. Top ten lists change quarterly after index rebalances: refresh after rebalance day to catch new mega cap weights. Some issuers publish full holdings CSV files if you need deeper analysis than top ten allows. For active ETFs, top ten may shift faster than index funds. Always use the same as of date when comparing two funds side by side.
How do I use this ETF overlap calculator on a phone or tablet?
Yes. ETF Overlap Detector runs entirely in your mobile browser with the same formulas as desktop. Optional localStorage may remember inputs on your device when enabled in browser settings.
Where is my data stored when I use ETF Overlap Detector?
Nowhere on our servers. Calculations execute locally in your browser. Optional localStorage saves form fields on your device only and never transmits portfolio numbers over the network.
Should I rely on ETF Overlap Detector for tax or legal decisions?
No. ETF Overlap Detector provides educational math only. Tax law, account rules, and personal circumstances vary. Consult a qualified tax or legal professional before transactions with material consequences.
Related Tools
Run Portfolio Rebalancer to redeploy overlap savings, Portfolio Beta to check risk after consolidation, ETF Expense Ratio to quantify fee stacking on duplicate funds, and Stock Chart to inspect shared mega cap names on portfolios.tools. Refresh holdings after quarterly index rebalances so overlap scores stay current.