Fund overlap is the share of holdings that two funds have in common, and it costs you in two ways: your risk is more concentrated than the number of funds suggests, and you may be paying a higher expense ratio for exposure you already own through a cheaper fund. Six funds that share most of their holdings behave more like two or three. You can measure overlap for free with the MarketXLS ETF Overlap Calculator and Mutual Fund Overlap Calculator: enter two tickers and you get the overlap percentage and the list of shared holdings with their weights, with no account required.
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What Is Fund Overlap?
Fund overlap happens when two or more funds in your portfolio hold the same underlying securities. It applies to both ETFs and mutual funds.
Some overlap is obvious:
- VOO and VFIAX are the same portfolio (S&P 500), just different wrappers
- SPY and IVV track the same index from different providers
But much overlap is hidden:
- VTI (total market) contains all of VOO (S&P 500) within it — about 80% overlap
- QQQ (Nasdaq 100) overlaps ~40% with SPY because the biggest Nasdaq stocks are also in the S&P 500
- FXAIX (Fidelity S&P 500) and VTSAX (Vanguard Total Market) share about 80% of holdings
Without a fund overlap calculator, you'd need to manually compare hundreds of holdings line by line. That's why tools exist.
The Real Cost of Fund Overlap
You May Be Paying Higher Fees for Exposure You Already Own
Each fund charges its expense ratio only on the money invested in that fund, so holding Apple through four funds does not multiply the fee on Apple. The cost comes from redundancy: if a 0.50% active large-cap fund mostly holds the same stocks as a 0.03% index fund you already own, most of that higher fee buys exposure you already have.
Your Risk Is Concentrated, Not Diversified
The whole point of owning multiple funds is diversification. But if they all hold the same top 20 stocks, a downturn in those stocks hits every fund simultaneously. Your "diversified" portfolio drops as if it were one concentrated bet.
Tax Harvesting Gets Complicated
Selling a fund at a loss and buying a substantially identical fund within 30 days before or after the sale triggers the wash sale rule, which disallows the loss for now. When you hold several near-identical funds across accounts, it is easier to trip that rule by accident, and harder to find a replacement fund that is similar but not substantially identical.
The ETF tax harvesting tool and mutual fund tax harvesting tool can help navigate these situations.
How to Check Fund Overlap
For ETFs
Use the ETF Overlap Calculator:
- Enter two ETF tickers (e.g., SPY and QQQ)
- Get instant overlap percentage
- See which stocks are shared and their weights in each fund
The tool covers 5,700+ ETFs and requires no account.
For Mutual Funds
Use the Mutual Fund Overlap Calculator:
- Enter two mutual fund tickers (e.g., VFIAX and VTSAX)
- Get the same detailed overlap analysis
- Works across 23,000+ mutual funds
For Mixed Portfolios (ETFs + Mutual Funds)
Many investors hold both, for example ETFs in a taxable brokerage account and mutual funds in a 401k. Run ETF pairs through the ETF calculator and mutual fund pairs through the mutual fund calculator, then compare the shared top holdings across the two results.
Real-World Overlap Examples
Let's audit a common portfolio:
The "set it and forget it" portfolio:
- VTSAX (Vanguard Total Stock Market) — IRA
- VOO (Vanguard S&P 500 ETF) — Taxable
- FXAIX (Fidelity 500 Index) — 401k
- QQQ (Nasdaq 100 ETF) — Taxable
Overlap analysis:
| Pair | Overlap |
|---|---|
| VTSAX vs VOO | ~80% |
| VOO vs FXAIX | ~99% |
| VTSAX vs FXAIX | ~80% |
| QQQ vs VOO | ~40% |
The verdict: Three of four funds are essentially the same thing (large-cap US equities). This investor thinks they have 4 diversified positions. In reality, they have one large-cap US bet and a tech-heavy tilt.
The fix:
- Pick one S&P 500 / total market fund across all accounts
- Replace duplicates with truly different asset classes:
- International stocks (VXUS or VTIAX)
- Bonds (BND or VBTLX)
- Small-cap value (VBR or VSIAX)
- REITs (VNQ)
A Framework for Interpreting Overlap
| Overlap % | What It Means | Action |
|---|---|---|
| 0-15% | Excellent diversification | Keep both funds |
| 15-30% | Good complement | Acceptable for most portfolios |
| 30-50% | Moderate overlap | Review — is the overlap intentional? |
| 50-75% | High overlap | Likely redundant — consider consolidating |
| 75%+ | Near-duplicate | Definitely redundant — drop one |
These bands assume both funds are doing the same job in the portfolio. Before acting on any percentage, it is worth knowing how fund overlap is calculated, because the same pair can score very differently depending on whether a tool counts holdings by name or weights them by position size.
Common Sources of Unintentional Overlap
Multiple Accounts, Same Strategy
Your 401k, IRA, and taxable account each have a "large-cap US" fund. Together, they triple your exposure to the same stocks.
Solution: Treat all accounts as one portfolio. Use different asset classes in different accounts based on tax efficiency.
"Diversifying" Within the Same Category
Owning 3 dividend ETFs (SCHD + VYM + DVY) feels diversified but creates 30-50% overlap. These funds all fish in the same pond of dividend-paying large-caps.
Solution: Pick the one dividend fund you like best. Add diversification through different categories, not more funds in the same category. Use the ETF comparison tool to pick the winner.
Target-Date Funds + Individual Funds
If your 401k has a target-date fund (which already holds US stocks, international stocks, and bonds), adding an S&P 500 fund on the side creates significant overlap with the equity portion of the target-date fund.
Solution: Either use the target-date fund exclusively, or build your own allocation from scratch. Don't mix both.
Total Market + S&P 500
VTI and VOO overlap about 80% because the S&P 500 constitutes the vast majority of the total US market by capitalization. You're not getting much additional diversification from the extra small and mid-cap stocks.
Solution: Pick one. VTI if you want the small/mid-cap exposure. VOO if you want pure large-cap.
How to Build a Low-Overlap Portfolio
A well-constructed portfolio should have minimal overlap between positions. Here's an example:
| Allocation | Fund | Overlap With Others |
|---|---|---|
| 40% US Large-Cap | VTI | Core position |
| 20% International | VXUS | <5% overlap with VTI |
| 15% US Bonds | BND | 0% overlap with equity |
| 10% Small-Cap Value | VBR | ~15% overlap with VTI |
| 10% REITs | VNQ | ~5% overlap with VTI |
| 5% International Bonds | BNDX | 0% overlap with BND |
Total portfolio overlap: minimal. Each position adds genuinely different exposure. Run any pair through the fund overlap calculator to verify.
Checking Overlap Regularly
Portfolio overlap isn't a one-time check. Fund holdings change as indices reconstitute, stocks enter or exit benchmarks, and active managers adjust positions.
Quarterly review: Run your fund pairs through the overlap calculator when you rebalance. It takes 5 minutes and can prevent drift into unintentional concentration.
Beyond Overlap: Finding Better Funds
If you discover overlap and need to replace a fund, these tools can help:
- ETF Screener: Filter 5,700+ ETFs by category, fees, returns, and more
- Mutual Fund Screener: Same depth across 23,000+ mutual funds
- Top ETFs by Buy Score: Curated list of highly-rated ETFs
Explore More FundXLS Tools
- ETF Overlap Calculator: overlap analysis between any two ETFs from 5,700+ ETFs
- ETF Comparison Tool: compare ETFs head-to-head on returns, fees, holdings, and risk
- Mutual Fund Comparison: compare mutual funds beyond past returns
- Mutual Fund Screener: filter 23,000+ mutual funds
Check Your Portfolio Overlap Now
Fund overlap takes a few minutes to check: enter two tickers and read the overlap percentage and shared holdings.
Try the Free ETF Overlap Calculator or the Mutual Fund Overlap Calculator
Both show the shared holdings, the overlap percentage, and each holding's weight in each fund. No signup required.
