FZROX vs FSKAX: 12 Key Differences [2026 Update]

Choosing between two nearly identical Fidelity index funds comes down to one key difference: cost. FZROX carries a 0.00% expense ratio while FSKAX charges 0.015% — a gap that sounds trivial but compounds over decades of investing. Both funds offer broad U.S. total market exposure, making this one of the most common decisions for Fidelity account holders. Detailed side-by-side data from PortfoliosLab confirms the funds track nearly identically over time. If you're building long-term wealth, pairing this decision with solid free budget templates can sharpen your overall strategy. Let's dive in!

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Summary Table

FZROX vs FSKAX: 12 Key Differences [2026 Update]

Below you'll find detailed information about each option, including what makes them unique and their key benefits.

1. Fund Names

FZROX and FSKAX are the two ticker symbols at the center of this comparison — both tracking the total U.S. stock market but offered by different providers. FZROX is Fidelity's ZERO Total Market Index Fund, while FSKAX is the Fidelity Total Market Index Fund. Understanding what each name represents helps investors quickly identify which fund fits their brokerage setup and investment goals.

Quick distinctions:

• FZROX: Fidelity ZERO Total Market Index Fund (proprietary index)
• FSKAX: Fidelity Total Market Index Fund (tracks Dow Jones U.S. Total Stock Market Index)

2. Expense Ratios

The expense ratio is arguably the most important factor when comparing FZROX vs FSKAX, directly affecting your net returns over time. FZROX carries a 0.00% expense ratio — literally zero cost — while FSKAX charges 0.015% annually. Though the difference seems trivial, on a $100,000 portfolio that's $15 per year, and the gap compounds meaningfully over decades of long-term investing.

Cost comparison:

• FZROX: 0.00% expense ratio (no annual fee)
• FSKAX: 0.015% expense ratio (~$15/year per $100,000 invested)

3. Assets Under Management

Assets under management (AUM) signal investor confidence and fund liquidity, both relevant when deciding between these two Fidelity total market funds. According to PortfoliosLab, FSKAX holds significantly more AUM than FZROX, reflecting its longer track record. FZROX launched in 2018 as part of Fidelity's ZERO fee initiative, so FSKAX's larger asset base simply reflects more years in the market rather than superior performance.

• Higher AUM generally means tighter bid-ask spreads and more stable fund operations
• Both funds are large enough that liquidity risk is negligible for retail investors

4. Number of Holdings

When comparing FZROX vs FSKAX, the number of holdings reveals a meaningful structural difference between the two funds. FSKAX holds approximately 2,700+ stocks covering virtually the entire U.S. market, while FZROX holds around 2,500+ securities. Both provide broad diversification, but FSKAX's slightly larger footprint means marginally greater exposure to micro-cap and small-cap stocks that FZROX may underweight or exclude entirely.

Key differences:

• FSKAX: ~2,700+ holdings, broader small/micro-cap coverage
• FZROX: ~2,500+ holdings, still diversified but slightly narrower universe

5. Inception Dates

Understanding each fund's inception date matters when evaluating long-term performance data in the FZROX vs FSKAX comparison. FSKAX launched in September 2011, giving it over a decade of tracked returns through multiple market cycles. FZROX launched in August 2018 as part of Fidelity's zero-expense-ratio lineup, meaning it has a shorter performance history — a factor worth noting when reviewing historical return comparisons.

Timeline snapshot:

• FSKAX inception: September 8, 2011
• FZROX inception: August 2, 2018
• FSKAX has ~7 additional years of trackable market data

6. YTD Returns

Year-to-date returns are one of the most closely watched metrics when deciding between these two total market index funds. Because both track the broad U.S. equity market — FSKAX following the Dow Jones U.S. Total Stock Market Index and FZROX following Fidelity's proprietary zero index — their YTD returns tend to be nearly identical, often differing by just 0.01–0.05 percentage points. According to PortfoliosLab, long-term annualized returns between the two funds are virtually indistinguishable for most investors.

• Short-term YTD differences are typically negligible (<0.1%)
• Both funds closely mirror overall U.S. stock market performance

7. 1-Year Returns

Over the most recent 1-year period, FZROX and FSKAX have delivered nearly identical results, which is expected given their near-identical holdings. Both funds track the total U.S. stock market, so short-term return differences typically fall within a few basis points. According to PortfoliosLab, any gap between the two is statistically insignificant for most investors.

• Returns differ by less than 0.10% in most recent 1-year windows
• Short-term tracking closely mirrors the broad U.S. market index

8. Dividend Yields

When comparing these two total market funds, dividend yield differences are minimal but worth noting for income-focused investors. FSKAX and FZROX both distribute dividends quarterly, drawn from the same broad basket of U.S. equities. According to PortfoliosLab, their yields typically land within 0.05–0.1% of each other in any given year.

• Both yield approximately 1.3–1.6% annually depending on market conditions
• FSKAX may distribute slightly higher dividends due to broader index sampling

9. Volatility

Volatility between FZROX and FSKAX is nearly indistinguishable because both track the total U.S. equity market. Their standard deviation and beta scores move in near-perfect lockstep, meaning neither fund carries meaningfully more risk than the other. For investors deciding between the two, volatility alone is not a differentiating factor.

• Both funds have a beta close to 1.0 relative to the broad market
• Drawdowns during corrections (e.g., 2020, 2022) were virtually identical across both

10. Minimum Investments

Both funds are accessible to virtually any investor, but this comparison point matters when deciding where to open an account. FZROX requires a $0 minimum investment and is exclusive to Fidelity accounts, while FSKAX also has no minimum at Fidelity. Neither fund charges a transaction fee at Fidelity, making both ideal for small or beginning investors building positions gradually.

Key differences:

• FZROX: $0 minimum, Fidelity-only, zero expense ratio
• FSKAX: $0 minimum, available at Fidelity, 0.015% expense ratio
• FSKAX can be held at other brokerages; FZROX cannot be transferred out

11. Tax Efficiency

When comparing these two total market index funds, tax efficiency is nearly identical — both are passively managed and generate minimal capital gains distributions. However, FZROX's zero-fee structure and slightly different index methodology can result in marginally fewer taxable events. According to White Coat Investor, neither fund has a meaningful tax advantage over the other for most investors holding in taxable accounts.

Tax considerations:

• Both funds distribute qualified dividends taxed at lower capital gains rates
• Low portfolio turnover in both keeps annual capital gains distributions minimal
• Tax-loss harvesting: FSKAX's transferability makes it slightly more flexible

12. Recommendation for US Investors

For most US investors choosing between FZROX and FSKAX, the decision comes down to portability versus cost. If you plan to stay at Fidelity long-term, FZROX's 0% expense ratio gives it a slight edge. If there's any chance you'll transfer your brokerage account in the future, FSKAX's broader compatibility makes it the safer pick. As noted at PortfoliosLab, long-term performance between the two is nearly indistinguishable.

Bottom line:

• Stay at Fidelity forever → FZROX (zero fees, same exposure)
• May switch brokerages → FSKAX (transferable, still ultra-low cost)

Final Words

Your best bet depends on whether you prioritize slightly lower fees with FZROX or broader accessibility with FSKAX — both are excellent long-term holds. Pair your choice with top expense tracking apps to keep your investment contributions consistent.