Methodology
How ETF Overlap Checker calculates overlap, updates ETF data, and turns holdings into compare pages.
How Overlap Is Calculated
A straightforward approach used by portfolio analysts.
For every stock that appears in both ETFs, we take the smaller of the two weights. Adding up all those minimums gives the total overlap percentage. A score of 100% means the two ETFs hold the exact same stocks in the same proportions.
Want the full explanation? Read the methodology page.
What the score means
For each shared holding, we take the smaller portfolio weight between the two ETFs. Adding those minimum weights produces the final overlap score. This keeps the metric practical: it measures duplicated exposure, not just whether the same stock appears in both funds.
Data and freshness
ETF metadata and holdings are imported from Financial Modeling Prep. Compare results are cached and refreshed when stale, with a target refresh window of 7 days. Each compare page also shows the latest holdings update dates used for the underlying funds.
Important limitations
This tool is built for clarity, not portfolio optimization advice. Holdings files can lag real-time portfolio changes, some providers may not publish all data at the same cadence, and bond ETFs may have less useful overlap data if holdings are unavailable from the upstream source.
How to use it well
Use overlap pages to sanity-check diversification before holding two ETFs together. If the overlap verdict is high or very high, the second fund may be adding less diversification than the label suggests.