VTI vs VOO: How Much Do They Really Overlap?

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 Short Answer: Overlap by Weight, Not by Count

VTI and VOO are two of the most popular ETFs on the market, and many investors hold both in the same portfolio — often believing they complement each other. The data tells a different story.

The live VTI vs VOO comparison, computed from current holdings, shows 502 shared holdings and a weighted overlap of 88.45% — a Very High Overlap verdict. Effectively every stock in VOO is also found in VTI.

That number deserves attention. If you hold both VTI and VOO in equal portions, the great majority of every dollar — 88.45% of the weight — is doing the same work in both funds.

Why Is the Overlap So High?

VTI tracks the CRSP US Total Market Index, which covers roughly 3,500 U.S. stocks including large-, mid-, and small-caps. VOO tracks the S&P 500 — the 500 largest U.S. companies by market capitalization.

Because market-cap weighting puts the heaviest emphasis on the biggest companies, those 500 S&P 500 names account for the vast majority of VTI's total weight. Small- and mid-cap stocks that are unique to VTI collectively represent only about 12–15% of VTI's total portfolio weight — even though they make up roughly 86% of VTI's holding count.

The result: VTI holds 7x more companies than VOO, but the additional ~3,000 names barely move the needle on weighted exposure.

Shared Top Holdings

The largest overlapping positions illustrate the concentration clearly — a few megacaps carry most of the shared weight.

Only the smaller of each pair of weights counts toward the score. The differences are slight because VOO is pure large-cap, so each megacap takes up a marginally larger slice than it does inside VTI's much longer holdings list.

What's Actually Different Between Them?

The real difference lives in the mid- and small-cap exposure that VTI holds and VOO does not. These segments include companies in the Russell 2000 range — regional banks, biotech startups, smaller industrials — that have historically shown different return characteristics from large caps.

Over rolling 10-year periods, the performance difference between VTI and VOO is typically less than 0.5% per year. In strong large-cap environments (like the AI-driven bull market of 2023–2025), VOO has often had a slight edge. When small caps outperform — as they did in 2016 and 2021 — VTI pulls ahead.

Neither fund has consistently dominated the other over full market cycles.

Should You Hold Both?

Holding both VTI and VOO in the same account provides almost no additional diversification. You are effectively paying two expense ratios (both 0.03%) to get nearly identical exposure. The small differentiation is too minor to justify the complexity.

Choose VTI if you want broad U.S. market exposure that includes all market caps in one fund.

Choose VOO if you specifically want the S&P 500's large-cap-only exposure, perhaps because you plan to pair it with a dedicated small-cap fund like VB or IJR.

Avoid holding both unless you have a deliberate, quantified reason to tilt toward large caps — in which case a targeted allocation to VOO alongside a smaller position in VXF (extended market) gives you cleaner control.

How to Verify Your Own Overlap

If you're unsure how much overlap exists in your own portfolio, you can open the live VTI vs VOO comparison — or run any pair you own at etf-checker.org — to see the weighted overlap score and shared holdings side by side — so you can decide whether the second fund is genuinely adding diversification or just doubling down on the same positions.

The 88.45% overlap figure should be the starting point for any honest evaluation of a VTI + VOO portfolio. Clarity here can simplify your holdings and potentially free up room for genuinely complementary exposure.