FXAIX — Fidelity 500 Index Fund
What FXAIX holds, how it works, who it fits, and how it compares
FXAIX is the ticker for Fidelity 500 Index Fund, an index mutual fund from Fidelity built to follow the S&P 500 (large U.S. companies). This page walks through what the fund actually holds, how its index works, who tends to use it, how it stacks up against VFIAX and other lookalikes, and the mechanics of buying it. Everything here is educational — none of it is a recommendation to buy or sell.
What FXAIX is
Buying FXAIX means buying a share of a pooled fund that owns, or closely mirrors, a basket of securities defined by published index rules. You are not picking individual companies and the fund manager is not either — the index decides what goes in and how much of it.
FXAIX is Fidelity’s S&P 500 index fund and one of the most common options you will find on a workplace retirement menu. For millions of people it is the default equity holding in their 401(k), often without their having chosen it deliberately.
Fidelity dropped the minimum investment to zero on its index funds and priced them at or below rivals, which makes FXAIX unusually accessible for someone starting with a small first contribution.
- Issuer: Fidelity
- Tracks: the S&P 500 (large U.S. companies)
- Style shorthand: broad U.S. large-cap
- Wrapper: an index mutual fund, so orders fill once a day at the closing net asset value
- Typical role in a portfolio: a core U.S. stock holding
How FXAIX works
An index is a published list of securities plus a rule for how much of each to hold. FXAIX aims to match that list closely enough that its results resemble the index minus costs. Small gaps between the two — tracking difference — come from fees, cash held between trades, and the practical cost of buying thinly traded positions.
As an index mutual fund, FXAIX is priced once daily at net asset value. Inside a 401(k) that is invisible to you — payroll contributions simply buy shares at the next close — which is part of why mutual funds remain the standard vehicle in employer plans.
The underlying index is identical to the one behind VOO, IVV, and VFIAX. Any performance difference between these funds over a year comes down to fees and small tracking effects, not to different investment decisions.
As a mutual fund, FXAIX does not trade during the day. You submit an order in dollars or shares and it fills at the net asset value struck after the close. There is no bid-ask spread and no premium or discount to worry about, but there is also no way to react to an intraday move — which for long-term investors is closer to a benefit than a limitation.
Costs come in two flavors. The expense ratio is the annual fee skimmed from assets, quoted as a percentage and deducted continuously rather than billed. Then there are transaction frictions: bid-ask spreads and any commissions for ETFs, minimum investments and potential short-term redemption rules for mutual funds. Low cost is a real advantage, but it is one input among several rather than the whole decision.
Who FXAIX is for
FXAIX provides broad U.S. large-cap exposure through Fidelity. Whether that belongs in your portfolio depends on your time horizon, what you already own, which accounts you have available, and how you behave when markets drop — not on how often the ticker appears in headlines.
FXAIX is the obvious pick for someone whose accounts live at Fidelity or whose employer plan offers it. The zero minimum makes it practical for a first IRA contribution of any size.
It travels poorly. Fidelity’s proprietary mutual funds generally cannot be moved in kind to another brokerage, so leaving Fidelity with a taxable position could force a sale and a tax bill. If you expect to change brokerages, an ETF avoids that friction entirely.
Three questions are worth answering before you decide. What specific job would this holding do — growth, ballast, income, or geographic diversification? How long can the money stay invested without being touched? And what do you already own that covers the same ground?
FXAIX vs peers
The funds most often mentioned alongside FXAIX are VFIAX (Vanguard 500 Index Fund Admiral Shares), SWPPX (Schwab S&P 500 Index Fund). The useful question is not which one is “best” in the abstract, but which small differences actually matter for what you are trying to do.
Against VFIAX, the differences are minimum investment, the brokerage you are tied to, and the absence of an ETF share class. Holdings and index are the same.
Against SWPPX, this is the Fidelity-versus-Schwab version of the same question. Neither firm has a meaningful cost advantage worth switching brokerages over; pick the one matching where your money already sits.
When you compare any two funds in this category, look at index methodology first — what is included and excluded, and how holdings are weighted. Then compare the expense ratio, the minimum investment, liquidity and spreads for ETFs, tax treatment in the account you plan to use, and whether you can move the position to another brokerage without selling it.
How to buy FXAIX
Once you have an account that offers it, purchasing FXAIX is mechanical. The steps below are educational and describe the process, not a suggestion that you should take it.
- Confirm the fund is available in your brokerage account or employer plan menu.
- Search ticker FXAIX and read the prospectus and share-class details.
- Check the minimum initial investment for the share class, and whether a lower-minimum class or ETF equivalent exists.
- Enter a dollar amount rather than a share count — mutual funds handle fractional shares automatically and your full contribution gets invested.
- Set up an automatic recurring purchase if consistency is your weak point, then leave it alone.
Inside a 401(k), your real decision is usually the contribution rate and the allocation percentage, not the ticker — the plan menu has already narrowed the field. Check whether your plan uses a collective trust version of the same strategy, which sometimes costs even less.
Before you place the order, make sure the money is genuinely long-term. Keep an emergency fund in cash separately, know how this position overlaps with what you already hold, and have a rough plan for what you will do the first time it drops twenty percent — because at some point it will.