Best Total Bond Market Index Funds Of 2025

TIAA-CREF Bond Index Advisor is a core U.S. bond index fund that tracks the Bloomberg Barclay’s U.S. Aggregate Bond Index. The fund aims to get most of its total return from income, investing in a wide spectrum of intermediate-term debt.

Nuveen, parent of TIAA Investments, says TBIAX uses a quantitative strategy to minimize trading costs.

TBIAX’s diversified holdings of more than 8,500 bonds include government securities as well as mortgage-backed, commercial mortgage-backed and asset-backed securities. The bulk of the fund’s holdings are high-quality, investment-grade assets.

The fund has an average effective duration of about six years. Duration shows the expected price decline (or rise) of a bond or bond fund for each 1% rise (or fall) in interest rates. In TBIAX’s case, shareholders can expect the security to fall in value by about 6% for each 1% annual rise in interest rates, and vice versa.

The Northern Bond Index Fund is another portfolio that strives to approximate returns of the Bloomberg U.S. Aggregate Bond Index. One of the older bond index funds on our list, founded in February 2007, it charges an ultra-low expense ratio that helps boost returns.

NOBOX is one of three funds in our list that requires a minimum initial investment. In this case, it’s $2,500.

The fund owns roughly 3,300 bonds, which makes it well diversified. And NOBOX reports an average effective duration of roughly 7 years. The fund posts allocations of about 40% in U.S. Treasurys, roughly 25% in mortgage-backed securities and the bulk of the remainder in investment-grade corporate bonds.

NOBOX’s turnover of about roughly 45% benefits shareholders by adding higher yielding bonds to the portfolio as interest rates rise. There’s minimal default risk for this diversified, high-quality, intermediate bond index fund.

This share class of the Vanguard Total Bond Market Index Fund was founded back in 2001, making it the oldest fund on the list and one of the oldest index funds in the U.S. The fund’s oldest share class first opened in 1986. VBTLX tracks the Bloomberg U.S. Aggregate Float Adjusted Index, a widely followed proxy for the entire U.S. bond market.

The fund offers Vanguard Admiral Shares that require a $3,000 minimum initial investment, which could be cost prohibitive for some new investors.

VBTLX owns well over 10,000 bonds and has an average effective duration over about six years. The portfolio posts an allocation of roughly 45% to Treasury and agency bonds, about 20% to U.S. government mortgage-backed bonds and about 15% to debt from industrial issuers.

When this fund has a higher weighting in Treasurys and higher-rated debt than competitors, it can offer more stability during economic uncertainty or volatility. Cautious bond fund investors often seek refuge in a conservative portfolio amid market uncertainty.

Launched in February 2017, Schwab U.S. Aggregate Bond Index Fund is a strong contender for the very best total bond market index fund available.

Like the other funds on our list, it favors the intermediate U.S. bond market. But its 58% turnover ratio tops all but one fund on our list. That indicates a willingness to replace lower-yielding bonds with higher-rate assets more often than most rival funds as interest rates rise.

Also like most other funds on this list, SWAGX is benchmarked against the Bloomberg U.S. Aggregate Bond Index. The fund’s average effective duration of about six years is similar to peers’. It’s heavily weighted toward U.S. government and agency bonds, and it has a hefty allocation to mortgage-backed securities. The fund has lots of corporate bonds, and the entire portfolio resides within the investment-grade portion of the credit quality spectrum.

Shareholders seeking a low-fee intermediate bond fund, with no required minimum investment floor, issued by a well-regarded fund family will find it in SWAGX.

Debuting in June 2018, the Fidelity Sustainability Bond Index Fund is designed to meet the needs of shareholders who want an intermediate bond fund that pursues ESG investing goals. Sustainable investing aims to have a positive net impact on the environment and society. Investors who use sustainable investing look for companies led by managers who prioritize better corporate governance.

FNDSX holds debt that is in the Bloomberg MSCI U.S. Aggregate ESG Choice Bond Index, and it also follows the rules of the Bloomberg U.S. Aggregate Bond Index. As a result, the fund owns investment-grade fixed-rate debt issues, including government, corporate, asset-backed, and mortgage-backed securities that meet certain ESG standards.

FNDSX’s average effective duration is about six years. The turnover ratio of 55% is the second highest on this list.

This is the second of three Fidelity total bond market index funds on our list. Launched in May 2011, the Fidelity U.S. Bond Index Fund has 34% average annual turnover and an average effective duration of about six years.

The asset allocation hews towards competitive offers. FXNAX lists an allocation to U.S. Treasurys of about 40%. Mortgage backed security pass-throughs (which refers to income from underlying assets relayed to fund shareholders by the fund) and corporate bonds are the second and third largest allocations, both around the mid-20s percentage weighting area.

The fund offers expansive diversification with about 9,000 bonds. With minimal credit risk and a low expense ratio, FXNAX is a sound bond index mutual fund.

Introduced in March 2017, Fidelity Flex U.S. Bond Index Fund is designed to mirror the performance of the Bloomberg U.S. Aggregate Bond Index.

FIBUX has a 49% turnover ratio. That’s about 33% lower than its Morningstar category average. That keeps costs down. And it’s a clue that the fund is not loaded with bonds that it will need to dump once interest rates begin to ease–which could happen later this year.

With an average duration of about 6 years, shareholders can expect the security to fall in value by about 6% for each 1% annual rise in interest rates.

Treasurys, mortgage-backed security pass-throughs and corporate bonds are FIBUX’s three largest allocations.

One important caveat is attached to FIBUX. It is what Fidelity calls a Flex fund. Those funds have zero expense ratios. But Fidelity Flex funds are available only to certain fee-based accounts offered by Fidelity.