VOO vs. VTI: What Actually Differs
Updated ·3 min read·Reviewed by the StockTools.ai Research Team
- ▸VOO holds roughly the 500 largest US companies (the S&P 500). VTI holds several thousand — the same large caps plus small- and mid-cap companies.
- ▸Because large caps dominate market-cap weighting, VOO and VTI have historically moved almost in lockstep — high overlap, high correlation, but not identical portfolios.
- ▸Both are widely considered among the lowest-cost funds available, and both are common "one-fund" core holdings — cost is rarely the deciding factor between them.
- ▸For most long-term investors this is not a "which is better" decision. Either is a reasonable simple core holding, and the difference shows up mostly in how you think about small-cap exposure, not in outcomes.
What each fund actually holds
VOO is a large-cap fund by design. It tracks the S&P 500, an index built from roughly the 500 biggest publicly traded companies in the US, selected and weighted by a committee using rules around size, profitability, and liquidity. If a company is not among the largest names in the market, it is simply not in VOO.
VTI takes a different approach: it aims to hold essentially the entire investable US stock market, which in practice means several thousand companies across large, mid, and small capitalizations. The top of VTI's portfolio looks almost identical to VOO's — the same mega-cap names dominate both — but VTI keeps going further down the size spectrum, adding companies VOO never touches.
Why they still move so similarly
Both funds are market-cap weighted, meaning bigger companies get bigger slices of the portfolio. Since the largest handful of US companies make up a substantial share of the entire market's value, they also make up a substantial share of VTI — not just of VOO. That shared core is why the two funds have historically tracked each other closely: when the giants move, both funds move, because both are heavily anchored to the same names.
The gap between them shows up in the smaller slice VTI carries that VOO does not — small- and mid-cap stocks. That slice does not usually move in a totally different direction from large caps, but it does not move identically either. Small caps can lead or lag large caps for stretches, which is why VOO and VTI are highly correlated but not the same thing. Over some periods they will diverge slightly; over others they will land nearly on top of each other.
The practical differences that actually matter
Cost is usually a non-issue here. Both funds are among the lowest-cost options available in the entire ETF industry, and Vanguard has built its brand around keeping both of them cheap. If you are choosing based on expense ratio alone, you are optimizing a difference too small to change your outcome.
The more meaningful distinction is exposure. VOO gives you the most-quoted, most-referenced index in American investing — useful if you want your portfolio to track "the market" in the way it is discussed on the news. VTI gives you that same large-cap core plus a standing allocation to small- and mid-cap companies, which some investors want because those segments can behave differently across a full market cycle and because "total market" is a more complete definition of owning US stocks. Neither reason is wrong; they reflect different priorities, not different quality.
So which one should you actually pick
Here is the honest answer: for most long-term investors, this choice matters far less than the amount of attention it gets. Because of how much the two funds overlap, their long-run performance has historically landed close to each other — not identical, but close enough that the decision rarely makes or breaks a retirement plan. This is a "either is a fine simple core holding" situation, not a "one is clearly better" situation.
If you want the simplest possible framing, pick VOO for the S&P 500 specifically, or pick VTI if you would rather own the whole market including smaller companies in one fund. Either choice, held consistently and paired with reasonable saving and cost discipline, will get most investors to a similar place. Where people actually lose ground is switching back and forth between the two chasing whichever one performed better recently — not in picking one and staying with it.
FAQ
Is VTI just VOO plus small caps?
Roughly, yes. VTI's large-cap holdings look very similar to VOO's because both are market-cap weighted and dominated by the same largest companies. VTI then extends further down into mid- and small-cap stocks that VOO does not hold at all.
Which has performed better, VOO or VTI?
Their long-run results have historically been close, given how much overlap exists between them, though the exact relationship shifts depending on whether small- and mid-cap stocks are outperforming or underperforming large caps during a given stretch. Neither has a consistent, reliable edge over the other.
Are VOO and VTI both low-cost?
Yes. Both are widely considered among the cheapest broad-market funds available, which is a large part of why they are both so popular as core portfolio holdings.
Can I just hold both VOO and VTI?
You can, but it adds redundancy rather than real diversification, since VTI already contains essentially the same large-cap companies VOO holds. Most investors pick one as a core US equity holding rather than layering both.
Does it matter more once my portfolio gets bigger?
Not fundamentally. The overlap between the two funds does not shrink as your account grows. What matters more at any size is sticking with a choice, keeping costs low, and not switching funds based on short-term performance chasing.
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Educational only — not financial advice. Concepts simplified for clarity; markets are messier than definitions.