ETF Overlap Calculator

What Is ETF Overlap?

Two ETFs can have completely different names and strategies while still holding a lot of the same underlying stocks — a US total market fund and an S&P 500 fund, for instance, will overlap heavily in their largest holdings. Overlap percentage measures how much of your money would effectively be duplicated if you held both funds, which matters for actual diversification: owning five funds that all hold the same mega-cap stocks isn't as diversified as it looks.

How to Use This Calculator

This calculator doesn't pull live fund data — instead, you look up each ETF's published holdings (available on the provider's website or on financial data sites) and enter the weight of each holding that appears in both funds. List each shared holding once, with its percentage weight in Fund A and Fund B. Holdings unique to just one fund don't need to be listed since they don't contribute to overlap.

How We Calculate It

For each holding, the overlap contribution is the smaller of its two weights — if a stock is 7% of Fund A and 4% of Fund B, only 4 percentage points can actually be "overlapping" between the two funds. Total overlap is the sum of these smaller values across every shared holding.

A Few Notes

Accuracy here depends entirely on how many holdings you enter — funds often hold hundreds of positions, and this calculator only totals what you've listed, so leaving out smaller shared holdings will understate the true overlap. For a full picture, prioritize each fund's largest 10-20 holdings, which typically account for most of the overlap between similarly-themed funds anyway.