VOO vs VTI: how these two index funds actually differ

VOO and VTI are two of the most talked-about index funds for beginners, and the short version is this: VOO tracks the S&P 500 (about 500 large US companies), while VTI tracks the total US stock market (roughly 3,500 or more companies, including smaller ones). They overlap heavily, so owning both at the same time is largely redundant. This article explains what each one is and how they differ. It is not a recommendation to buy either.

What VOO is

VOO is an exchange-traded fund (ETF) that follows the S&P 500. The S&P 500 is a list of around 500 of the largest publicly traded companies in the United States. When you own a share of VOO, you own a tiny slice of all of those companies at once, weighted by their size.

Because it holds the biggest companies, VOO is often described as a bet on large US businesses as a group. It is not a single stock. It is one fund that spreads your money across hundreds of companies, so no single company's bad day sinks the whole thing.

What VTI is

VTI is also an ETF, but it follows the total US stock market instead of just the largest 500 companies. That means it holds those same big companies plus thousands of medium-sized (mid-cap) and smaller (small-cap) ones. In total that is often 3,500 or more companies.

So VTI includes almost everything VOO includes, and then adds the smaller companies on top. If you picture VOO as the top layer of the US market, VTI is that same top layer plus the layers underneath it.

How much they overlap

This is the part that surprises a lot of beginners. The largest companies make up a big portion of both funds. Because those giant companies carry so much weight, VOO and VTI tend to move up and down very similarly day to day.

The smaller companies that VTI adds are many in number but small in total weight. They can nudge VTI's returns in one direction or another over long stretches, but they rarely make the two funds behave dramatically differently.

Here is the practical takeaway:

• VOO = large US companies only.
• VTI = large companies plus mid-size and small ones.
• The two share most of the same big holdings, so their results usually look alike.

That heavy overlap is exactly why holding both at once is often described as redundant. You would mostly be buying the same large companies twice, with a small extra sliver of smaller companies from VTI.

ottie: "you don't have to pick the 'perfect' one today. both are baskets of many companies, not a single bet. slow and steady is fine."

Fees and how they trade

Both VOO and VTI are known for very low expense ratios. An expense ratio is the small yearly fee a fund charges, shown as a percentage of the money you have invested. A low expense ratio means more of your money stays invested rather than going to fees. You can read more in our guide on how investment fees work.

Both trade like a stock during market hours, which means you can buy or sell shares while the market is open. Some brokerages also let you buy fractional shares, so you are not forced to have the full price of one share to get started.

So which one is for you

This is where it stays your decision, not ours. The honest summary is that VOO and VTI are close cousins. One is a broad slice of large US companies, the other is a broad slice of the entire US market. Neither is an individual stock bet, and neither is a shortcut to quick returns.

A few plain points that people weigh when they think it through:

1. Do you want only large companies, or the whole US market including smaller ones? That single question is the real difference.
2. Do you already hold something similar? If you own one broad US fund, adding the other mostly duplicates it.
3. How do the fees and available fractional shares compare inside your specific brokerage account?

There is no universal right answer, and you do not need to feel certain to keep learning. The point of this article is to make the difference clear, not to push you toward one ticker.

The bigger idea underneath both

VOO and VTI are both examples of broad, diversified index funds. Diversification means spreading money across many companies so that your outcome does not ride on any single one. Both funds do that by design, which is a large part of why beginners come across them so often.

If the terms here are new, that is completely normal. Understanding what an index is, what an ETF is, and how fees quietly add up over time will make this comparison feel much simpler. Those foundations matter more than memorizing which fund has a handful more companies.

Take your time, learn the pieces, and remember that understanding the tool is more useful than rushing to choose one. If you want gentle, beginner-friendly lessons that build this kind of understanding step by step, you can join the otter waitlist.