VOO vs IVV: Nearly Identical — So How Do You Choose?

Disclaimer: This content is not investment advice. Investing involves the risk of loss of principal. Past performance does not guarantee future results. Always consult a qualified financial advisor before making investment decisions.

The Vanguard S&P 500 ETF and the iShares Core S&P 500 ETF track the same index with the same methodology at nearly the same cost. The live VOO vs IVV comparison puts their weighted overlap at 97.16% across 477 shared holdings — a Very High Overlap verdict, and about as close to a true duplicate as two separate funds get.

That number settles one question and opens another. You almost certainly should not hold both. So which one?

What 97.16% Overlap Looks Like

Both funds cap-weight the S&P 500, so their largest positions line up almost exactly. Where a megacap sits at 7.56% in one fund, it sits at 7.58% in the other. Under the weighted formula the smaller figure counts, and the difference discarded is measured in hundredths of a percentage point.

Overlap = Σ min(weight in Fund A, weight in Fund B)

The residual few percent is not a strategy difference. It comes from ordinary mechanics: slightly different cash balances, timing of index changes, share-class and lot handling, and the small tail of positions each fund happens to hold on a given filing date.

Contrast that with two funds drawing from the same index under a different rule. RSP vs VOO shares 502 holdings — more than VOO and IVV share — yet scores only 46.49%, because RSP equal-weights. Shared tickers do not determine overlap. Shared weighting does.

Holding Both Adds Nothing

A Very High Overlap score at this level means the second fund is, for practical purposes, more of the first. There is no diversification benefit to capture, and a few real costs to carry:

• Two positions to rebalance where one would do.
• Two cost bases to track, and more complexity at tax time.
• A false sense of diversification in the portfolio summary — two line items that behave as one.

The only common reasons to end up holding both are structural rather than strategic: one sits in a 401(k) that offers a single provider, or selling the older position would realize a gain you would rather defer. Those are legitimate. "Spreading risk across two fund families" is not.

So What Actually Differentiates Them

When the portfolios are this close, the decision moves entirely off the holdings:

• Expense ratio. Both are at the floor of the large-cap index category, and the gap between them is small enough that it should rarely be the deciding factor on its own.
• Platform and ecosystem. Commission-free access, automatic investment features, and fractional-share support vary by brokerage and often favor one issuer.
• Liquidity and spreads. Both trade enormous volume. This matters to active traders and is close to irrelevant for buy-and-hold investors.
• Account context. Which fund your employer plan, robo-advisor, or existing tax lots already point to is usually the most practical tiebreaker.
• Tax-loss harvesting. Because they are 97.16% similar but not identical securities, investors sometimes use one as a harvesting partner for the other. Rules around substantially identical securities are genuinely unsettled here, so this is a question for a tax professional rather than a blog post.

The Broader Lesson

VOO and IVV are the reference point for what "the same fund twice" looks like in the data. Once you have seen 97.16%, other numbers become easier to read: a Low Overlap pairing like SCHD vs VYM at 18.89% is clearly doing two different jobs, and something in between deserves a closer look at which holdings drive the score.

For the scoring mechanics, see the ETF comparison methodology guide. To audit a whole portfolio rather than one pair, see how to reduce ETF portfolio overlap.

Conclusion

At 97.16% overlap across 477 shared holdings, VOO and IVV are interchangeable in a portfolio sense. Pick one on cost, platform, and account context — then spend the saved attention on the parts of your portfolio where the overlap question is still open.

Check any pair at ETF Overlap Checker — free, no account required.