Bond Funds Explained for Investors Who Only Own Stocks

In 2022 a broad US bond index fund lost about 13 percent, its worst calendar year in decades. Plenty of people who had bought it as the "safe" part of their portfolio were stunned. They had been told bonds do not lose money, and here was a statement showing a four figure drop.

That year is the best possible starting point for understanding bond funds, because it shows what they actually are and what they are not. If you already own a stock index fund and keep hearing that you should add bonds, this guide walks through bond funds explained in plain dollars: how they earn, why their price moves, which type to pick and when you might not need one at all.

Bond Funds Explained in One Paragraph

A bond is a loan. You lend money to a government or company, they pay you interest, and they return the principal on a set date. A bond fund pools money from thousands of investors and buys hundreds or thousands of these loans at once. You do not own any single bond to maturity. You own a slice of a constantly changing pile of them, and the fund's share price moves every day with the market value of that pile.

That last point is the one most beginners miss. An individual bond held to maturity pays back its face value. A bond fund has no maturity date, so its price can stay below what you paid for months or years.

Why a Bond Fund's Price Goes Down When Rates Go Up

Imagine you hold a bond paying 2 percent. New bonds suddenly pay 5 percent. Nobody will pay full price for your 2 percent bond when they can buy a 5 percent one, so its market value drops until its yield matches what is available.

Bond funds report a number called duration that tells you roughly how sensitive they are to this. A simple rule of thumb:

Fund duration	Approximate price change if rates rise 1 percentage point	On a $10,000 position
2 years (short term)	About minus 2 percent	About minus $200
6 years (intermediate)	About minus 6 percent	About minus $600
17 years (long term)	About minus 17 percent	About minus $1,700

The same math works in reverse. When rates fall, the fund's price rises by roughly the duration times the drop. And over time, higher rates mean the fund buys new bonds that pay more, so the income slowly makes up for the earlier price loss.

The Main Types of Bond Funds

Total bond market funds

These hold a mix of US Treasury, government agency and investment grade corporate bonds, usually with a duration around six years. For most first time bond buyers this is the default choice, and many charge expense ratios of 0.03 to 0.05 percent.

Treasury funds

Only US government debt. Lower yield than a total market fund but the least credit risk. Short term Treasury funds behave a lot like a savings account with small price wiggles.

Corporate bond funds

Loans to companies. They pay more than Treasuries because companies can default. Investment grade funds stick to stronger borrowers.

High yield funds

Loans to weaker companies. Yields are higher, and in a recession these funds can fall alongside stocks, which defeats much of the purpose of holding bonds.

Municipal bond funds

Loans to states and cities. Interest is generally free from federal income tax, which can make them worthwhile in a taxable account if you are in a 24 percent bracket or higher.

The Advice to Hold Your Age in Bonds Is Outdated for Many People

You will still read the old rule: hold your age in bonds, so a 30 year old should be 30 percent bonds. I think that rule is too blunt for most young investors.

Someone who is 30, has a steady job, a full emergency fund and 35 years until retirement can usually handle stock market swings. Putting 30 percent into bonds lowers their expected long term growth considerably for protection they may not need yet. Many target date funds for people in their 30s hold only around 10 percent in bonds.

A better question is this: how much could your portfolio fall before you would panic and sell? If a 35 percent drop in a $40,000 stock portfolio, a $14,000 loss on paper, would push you to sell, you probably need more bonds than your age suggests. If you would keep buying, you may need fewer. Your behavior matters more than your birthday.

What Bond Funds Actually Do in a Portfolio

Bonds are not there to beat stocks. They have three practical jobs:

Cushion. In most stock market crashes, high quality bonds have held their value or risen. In 2008, for example, broad US bond funds ended the year positive while stocks fell sharply.
Dry powder for rebalancing. When stocks drop, you can sell some bonds and buy stocks cheaply, then reverse the trade when stocks recover.
Money with a date on it. Cash you need in three to seven years, such as a house down payment, often fits better in a short term bond fund than in stocks.

The 2022 example is the exception worth remembering. When inflation drives rates up quickly, stocks and bonds can fall together. Diversification reduces risk but never removes it.

How to Buy Your First Bond Fund

Decide the account. Bond fund interest is taxed as ordinary income, so bonds often fit best inside a 401k or IRA, with stocks in your taxable account.
Pick a broad fund. A total bond market index fund or ETF is a sensible starting point.
Check the expense ratio. A difference of 0.40 percent sounds tiny, but on a $20,000 position that is $80 every year. Our breakdown of expense ratios explained in dollars shows how that adds up over decades.
Check duration and yield. Both are listed on the fund's page. Match duration roughly to when you might need the money.
Set a target mix and stick to it. Rebalance once a year or when your mix drifts more than 5 percentage points.

If you are still choosing your stock side, start with index funds explained for a first time investor and add bonds once that is in place.

Frequently Asked Questions

Can a bond fund lose money?

Yes. A bond fund's price falls when interest rates rise or when borrowers default. Short term and Treasury funds lose less in those situations than long term or high yield funds.

Is a bond fund better than a high yield savings account?

Not for an emergency fund. Savings accounts never drop in value. Bond funds suit money you will not need for at least a few years and can leave alone through a bad year.

How often do bond funds pay income?

Most pay monthly. You can take the payments as cash or reinvest them automatically, which most long term investors do.

The Takeaway for a Stock Only Investor

A single low cost total bond market fund, sized to how much of a drop you can sit through without selling, covers what most people need. Check the duration, keep the fund inside a tax advantaged account when you can, and rebalance once a year. More guides for beginners live in our investing basics section.