Get the app
Get the app

Join millions of investors on Stash

Investing, simplified

Start today with as little as $5
Get the app
Teach Me

What’s an Index Fund and How Do I Buy One?

May 02, 2019

5 min read

When it comes to investing, you have plenty of options. There are stocks, bonds, mutual funds, exchange traded funds (ETFs), and something called index funds, among other things.

But what is an index fund, exactly, and how do you invest in one?

It may sound pretty complicated, but it’s not. Read on and we’ll break it down for you.

What is an index fund?

Index funds are a type of mutual fund, which means they are pools of money collected from many investors at once, hence the word “mutual”.

They were popularized in the 1970s by the late mutual fund legend John Bogle, founder of the Vanguard Group. Before this, old-school mutual funds were handled by a professional money manager who picked a variety of stocks to invest in at once—and charged investors a pretty penny to do so.

Index funds, on the other hand, automatically invest in a specific group or “index” of stocks that are lumped together based on things like industry, company size, or geographical location. They can be a low-cost, hands-off way to participate in the stock market without having to pick individual stocks or pay a mutual fund manager to pick a basket of stocks for you.

For instance, many popular U.S. index funds follow the Standard & Poor’s 500 (S&P) or the Dow Jones Industrial Average (DJIA) indices. The performance of the index fund attempts to track the performance of the overall index itself, generally rising and falling along with the group.

Investing in an index fund can help you diversify—meaning that if one stock in the group falls, the investor could be protected by the presence of the other stocks in the group. And because such funds are not actively managed, they may have lower fees than traditional mutual funds, making them attractive for cost-conscious investors who are investing for the long term. One of the disadvantages of index mutual funds, however, is that, like all mutual funds, they are less “liquid” than individual stocks, because they only trade once a day, at the market close. Individual stocks, on the other hand, can be bought and sold virtually instantaneously, whenever the stock market is open.

ETF Index Funds

The creation of exchange-traded funds (ETFs) has simplified trading of index funds. ETFs are similar to index mutual funds in that they often correspond to an index or an industry sector—you can choose to invest broadly in technology or health care or energy, for instance, or just about anything else. But like stocks, ETFs can be bought and sold throughout the day and are not simply priced at the market close like traditional index mutual funds.

Now that you know what an index fund is, and their two basic kinds—index mutual funds and index ETFs—let’s get to the fun stuff: How to buy them!

The nuts and bolts: How can I invest in index funds?

Index funds are widely available through online and brick-and-mortar brokerages. Some brokerages specialize in index mutual funds, and some, like Stash Invest, specialize in ETFs, including index ETFs.

When you’re deciding which brokerage to use, it’s important to consider the selection of funds available to you—there are more than 10,000 ETFs and mutual funds out there—and the costs involved.

For instance, there are commission-free and no transaction fee choices available that can help save you money when you start investing. Also, consider how much the brokerage charges to buy or sell funds generally. Keep in mind that mutual fund fees may be higher than ETF fees.

Once you’ve picked a brokerage and opened an account (find out more about how to do that here), the next thing to do is pick an index. Many funds track the performance of the major U.S. indexes. The S&P 500 index is one of the most popular ones to invest in, because the 500 companies it tracks include large, well-known U.S. businesses across a variety of industries. It is considered a  gauge of the larger U.S. economy, and it’s often a benchmark against which other indexes are measured.

But the S&P 500 certainly isn’t the only game in town. There are indexes—and corresponding funds—based on all kinds of things. Here are a few major ones to consider:

Anything else I should consider?

Generally speaking, index funds are relatively low-cost, thanks to the high degree of automation involved. However, you shouldn’t assume that all index funds are cheap. As with any investment, it’s important to do your research before you buy. Look for things like expense ratio and tax-cost ratio.

Also, many brokerages have an account minimum, and mutual funds in particular often have an investment minimum—both of which can be thousands of dollars.

But if you’re a new investor without a lot of capital, don’t worry, there are also plenty of low-fee or no-fee options out there.

Get Stash

Stash lets you get started investing for just $5.

Investing, simplified.

Start today with as little as $5.

Get the App

Hooked on Stash? Tell your friends!

Get $5 for every friend you refer to Stash.

Refer friends

Hooked on Stash? Tell your friends!

Get $5 for every friend you refer to Stash.

Refer friends

By Rob Williams

Investment Profile

Bonds Worldwide

An International Bond ETF on Stash

Learn more
Explore more articlesChoose a topic to learn more about
Technology social media politics pop culture budgeting

This material has been distributed for informational and educational purposes only, represents an assessment of the market environment as of the date of publication, is subject to change without notice, and is not intended as investment, legal, accounting, or tax advice or opinion. Stash assumes no obligation to provide notifications of changes in any factors that could affect the information provided. This information should not be relied upon by the reader as research or investment advice regarding any issuer or security in particular. The strategies discussed are strictly for illustrative and educational purposes and should not be construed as a recommendation to purchase or sell, or an offer to sell or a solicitation of an offer to buy any security. There is no guarantee that any strategies discussed will be effective.

Furthermore, the information presented does not take into consideration commissions, tax implications, or other transactional costs, which may significantly affect the economic consequences of a given strategy or investment decision. This information is not intended as a recommendation to invest in any particular asset class or strategy or as a promise of future performance. There is no guarantee that any investment strategy will work under all market conditions or is suitable for all investors. Each investor should evaluate their ability to invest long term, especially during periods of downturn in the market. Investors should not substitute these materials for professional services, and should seek advice from an independent advisor before acting on any information presented. Before investing, please carefully consider your willingness to take on risk and your financial ability to afford investment losses when deciding how much individual security exposure to have in your investment portfolio.

Past performance does not guarantee future results. There is a potential for loss as well as gain in investing. Stash does not represent in any manner that the circumstances described herein will result in any particular outcome. While the data and analysis Stash uses from third party sources is believed to be reliable, Stash does not guarantee the accuracy of such information. Nothing in this article should be considered as a solicitation or offer, or recommendation, to buy or sell any particular security or investment product or to engage in any investment strategy. No part of this material may be reproduced in any form, or referred to in any other publication, without express written permission. Stash does not provide personalized financial planning to investors, such as estate, tax, or retirement planning. Investment advisory services are only provided to investors who become Stash Clients pursuant to a written Advisory Agreement. For more information please visit