What is ETF overlap?
Funds are wrappers; stocks are what you own. Overlap is the share of your money that lands in the same stocks no matter which wrapper you bought.
The definition that matters: weight overlap
For every stock held by both funds, take the smaller of the two weights, then add them up. Example: Fund A holds 3% Apple, Fund B holds 5% Apple → Apple contributes 3 percentage points to overlap. Do that across every shared holding and you get a single number: "X% of my money is in the same stocks either way."
You'll also see count overlap ("they share 101 of 102 holdings"). It's intuitive but misleading on its own: sharing many tiny positions matters little, while sharing a few giant ones matters a lot. Always look at weight.
Why it sneaks up on people
US index funds are market-cap weighted, so the same handful of mega-caps dominates most broad funds. An S&P 500 fund plus a total-market fund plus a growth fund feels like three bets — but the top ten names of all three are nearly identical. The diversification you see on your statement (three funds!) is not the diversification you actually own.
How much overlap is too much?
Rules of thumb we use on our pair pages:
| Weight overlap | Reading |
|---|---|
| 70%+ | Effectively the same portfolio — holding both adds little except complexity |
| 30–70% | Related but distinct — fine if intentional; check which names double up |
| Under 30% | Genuinely different exposures — combining them actually diversifies |
Context matters: an S&P 500 fund and a tech sector fund should overlap — the question is whether you meant to double your tech bet.
Check it in ten seconds
Every comparison on this site is computed from official issuer holdings files — see a few popular ones below, or enter your whole portfolio to see your true combined exposure.
FAQ
What is ETF overlap?
ETF overlap measures how much two funds hold the same underlying stocks. The standard metric is weight-based overlap: for every stock held by both funds, take the smaller of the two portfolio weights, then sum. The result is the share of your money that ends up in the same stocks whichever fund you buy.
What is the difference between weight overlap and count overlap?
Count overlap is the number of shared holdings (e.g., "two funds share 101 of 102 stocks"). Weight overlap accounts for position sizes and is the number that matters for diversification: two funds can share only 30 names but if those names are the top positions of both, the weight overlap — and your concentration — is high.
Does ETF overlap matter?
Yes, when your goal is diversification. Buying two funds that hold the same mega-cap stocks concentrates your portfolio while feeling diversified. Overlap itself is not bad — sometimes you want doubled exposure — but you should know it exists rather than discover it in a drawdown.