Portfolio Overlap Calculator
Paste two portfolios. See how much they actually overlap, fund by fund down to the companies and bonds inside. SPY and VTI are different tickers, but they hold the same 500 companies.
One ticker and weight per line (e.g. SPY 60). Weights can be %, decimals, or any unit; the tool normalizes to 100%.
Same format. Order does not matter. Duplicate tickers keep the first row.
Counts only tickers that appear in both lists. SPY and VTI count as 0% here.
How the look-through works
Every US fund and ETF files its full holdings with the SEC each quarter (Form N-PORT). The calculator reads each fund through its latest filing and applies the classic rule one level down: overlap = sum of min(weight_A, weight_B) for every shared holding. A stock counts once whichever fund holds it, and share classes of one company count together.
Bonds match by issuer and maturity band, so a 20-year Treasury and a 3-month bill do not count as the same thing. Cash, securities-lending collateral and derivatives are left out; leveraged funds count at their multiple (TQQQ is 3 times QQQ's holdings) and inverse funds add nothing. SPY files no N-PORT (it is a unit trust), so it is read through IVV, which tracks the same S&P 500. Gold trusts share one gold exposure; commodity and managed-futures funds are compared as their own exposure, because their filings list collateral rather than what they track.
Holdings are as of each fund's latest filing, typically 1 to 3 months old; index funds change little in that time. The page shows how each fund was read, and anything it could not look through is listed rather than guessed.
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Past performance is not indicative of future results. Overlap is a diversification metric, not a return forecast. Holdings come from public SEC filings and may be out of date. Always do your own research before investing.
Portfolio Overlap Calculator: Frequently Asked Questions
- How is portfolio overlap calculated?
- The calculator normalizes each portfolio's weights to 100%, then reads every fund through its holdings, from the SEC N-PORT filing each US fund files quarterly. It sums the smaller of the two weights for every company, bond issuer and maturity band, or exposure (such as gold) that both portfolios hold. 0% means nothing in common, 100% means the same holdings. SPY and VTI, for example, share about 88%, although they are different tickers. The same-ticker overlap is shown beside it for reference.
- How much portfolio overlap is too much?
- There is no universal threshold; the percentage is the share of your money sitting in the same underlying holdings in both portfolios. The higher it is, the less the second portfolio adds beyond the first. It is worth checking before blending two strategies, because a blend of heavily overlapping strategies diversifies less than the strategy count suggests.
- Does overlap measure correlation?
- No. Overlap counts shared holdings by weight, while correlation measures how returns move together. The calculator shows both: the look-through overlap, and the correlation of the two portfolios' daily returns over the last 3 years. Different holdings can still move together (US large caps and US small caps), which is why the second figure is there.
- Does the overlap tool work for European and UCITS ETFs?
- Partly. UCITS funds do not file SEC N-PORT reports, so a UCITS ETF that tracks exactly the same index as a US fund (CSPX and the S&P 500, for instance) is read through that US fund's holdings. Other UCITS tickers are listed as not looked through, and only their same-ticker overlap counts.
- Do I need an account to use the overlap calculator?
- No. The tool is free and needs no signup. The tickers and weights you paste are sent to BestFolio's server to read the funds' holdings; the portfolios themselves are not saved.
- Can I compare my portfolio against a TAA strategy's allocation?
- Yes. Paste the strategy's current allocation as Portfolio B, one ticker and weight per line. BestFolio publishes current allocations for 6 strategies free without an account, so you can check how much a tactical strategy overlaps what you already hold.