Fidelity US Bond Index Fund
Figures last verified October 31, 2026
Tracks the Bloomberg US Aggregate Bond Index — investment-grade US government, corporate, and securitized bonds.
FXNAX is the Aggregate index — the same 'Agg' that VBTLX tracks — at 0.025% with no minimum, making it the cheapest of the big three total-bond funds. Thousands of investment-grade bonds, intermediate duration, the government-heavy mix that makes the Agg behave like ballast rather than a return engine.
There is no zero-fee bond fund in Fidelity's lineup, and 2.5 basis points is close enough. The real decisions sit above the fund level: how much in bonds at all (your age, nerves, and timeline), and where to hold them (tax-advantaged accounts, almost always, since bond interest is taxed as ordinary income). Once those are settled, FXNAX versus VBTLX versus SWAGX is a coin flip with three identical sides.
The bond slot of a Fidelity three-fund portfolio.
FXNAX alternatives & comparable funds
If you’re weighing FXNAX against the field, these are the funds most investors line it up against — same job, different provider, slightly different terms.
| Fund | Family | Expense Ratio | Minimum |
|---|---|---|---|
| FXNAX — Fidelity US Bond Index Fund | Fidelity | 0.025% | $0 |
| VBTLX — Vanguard Total Bond Market… | Vanguard | 0.05% | $3,000 |
| SWAGX — Schwab US Aggregate Bond Index Fund | Schwab | 0.04% | $0 |
| MWTRX — Metropolitan West Total Re… | Metropolitan West | 0.65% | $5,000 |
Head-to-head comparisons
Frequently asked questions
What is the expense ratio of FXNAX?
FXNAX (Fidelity US Bond Index Fund) has an expense ratio of 0.025%, which works out to roughly $2.50 per year for every $10,000 invested. That is very low by industry standards, where the average fund still charges well over 0.40%.
What is the minimum investment for FXNAX?
FXNAX has no minimum initial investment — you can start with any amount.
What does FXNAX invest in?
Tracks the Bloomberg US Aggregate Bond Index — investment-grade US government, corporate, and securitized bonds. It falls in the bond category and is an index fund.
What are good alternatives to FXNAX?
The funds most often compared with FXNAX are VBTLX, SWAGX, MWTRX — broadly similar exposure from different providers, with small differences in fee, minimum, and portability that usually come down to which brokerage holds your account.
Expense ratio and minimum for FXNAX drawn from Fidelity fund documentation; last verified October 31, 2026. Figures change — confirm against the official prospectus before investing. This review is editorial opinion, not investment advice.