FZROX vs FXAIX: Total Market or S&P 500 at Fidelity in 2026?

This is really the classic total-market vs S&P 500 question, asked inside Fidelity. FXAIX (Fidelity 500 Index Fund) tracks the S&P 500 for 0.015%. FZROX tracks Fidelity's U.S. Total Investable Market Index for 0.00%. Because both are market-cap weighted, the S&P 500 companies make up most of FZROX too; the difference is the mid- and small-cap slice that only FZROX owns.

Over the five years ending September 2026, FXAIX returned 13.77% a year and FZROX 12.79%, with similar volatility (15.6% vs 16.0%). That gap reflects the index, not the fees: mega-cap stocks outperformed smaller companies over the period. Over longer stretches the two have traded leadership, which is why many investors choose based on philosophy rather than recent returns.

The fee difference is $15 a year per $100,000, small enough to ignore for most people. FXAIX pays dividends quarterly; FZROX pays once a year in December. The bigger practical difference is access: FXAIX shows up in many workplace plans and at other brokerages, while FZROX is limited to Fidelity accounts.

Want to own the whole market for free in a Fidelity IRA? FZROX. Prefer the S&P 500 benchmark, or need a fund you can keep if you change brokers? FXAIX. Holding both adds little, since FZROX already contains everything in FXAIX. Pick one as your core U.S. holding and add international exposure (such as FZILX or VXUS) separately.