Best Index Funds 2026: 5 Compared on Cost and Coverage

WriterPickly Editorial

Updated 2026-09-10

SourcedLast reviewed 2026-09-10AI-drafted desk research based on public specs, manufacturer data and independent reviews — not hands-on tested

Expense ratios have converged so close to zero that picking the wrong index fund now costs you almost nothing — and yet the differences in tax efficiency, portability, and trading mechanics still matter over decades. These five funds cover nearly the same market but serve different investors in meaningfully different ways. Here is what separates them after you strip away the marketing.

Quick answer

For most taxable accounts, VTI is the pick — 3,700+ US stocks at a 0.03% expense ratio, and the ETF structure lets Vanguard flush unrealized gains for better tax efficiency than a mutual fund. Fidelity's FZROX is the cheapest fund in existence at 0.00% but tracks a proprietary index and is not portable, SWTSX allows dollar-based automatic investing at Schwab, and SCHB is Schwab's tight-spread ETF answer to VTI.

Check price: Vanguard Total Stock Market ETF (VTI) →

📋How we compared

Funds evaluated on five criteria: expense ratio, fund size and liquidity, tax efficiency (ETF structure vs mutual fund), brokerage portability, and historical tracking error vs the target index.

📋

Funds evaluated on five criteria: expense ratio, fund size and liquidity, tax efficiency (ETF structure vs mutual fund), brokerage portability, and historical tracking error vs the target index.

★ Best Pick

Vanguard Total Stock Market ETF (VTI)

$0.03Reference price

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Best Overall: VTI holds 3,700+ US stocks at 0.03% ER and is the default recommendation for taxable brokerage accounts. Its ETF structure means Vanguard can flush unrealized gains in-kind, and the fund has issued zero capital gains distributions since 2000.

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Top picks ↓

1
Vanguard Total Stock Market ETF (VTI)
A+Best Overall
$0.03Reference price
View deal →
2
Fidelity ZERO Total Market Index Fund (FZROX)
ALowest Cost
$0Reference price
View deal →

Product	Price	Link
1Vanguard Total Stock Market ETF (VTI)A+Best Overall	$0.03Reference price	View deal →
2Fidelity ZERO Total Market Index Fund (FZROX)ALowest Cost	$0Reference price	View deal →

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1★ Best PickA+Best OverallVanguard Total Stock Market ETF (VTI)

Available at Vanguard, Fidelity, Schwab, and most brokerages. No minimum at most brokers.

VTI holds 3,700+ US stocks at 0.03% ER and is the default recommendation for taxable brokerage accounts. Its ETF structure means Vanguard can flush unrealized gains in-kind, and the fund has issued zero capital gains distributions since 2000. Works at any brokerage, trades with spreads under $0.02.

Pros

✓Zero capital gains distributions since 2000
✓Holds at any brokerage — fully portable
✓Ultra-tight bid-ask spread, $400M+ daily volume

Cons

✗0.03% ER vs FZROX's 0.00% — tiny but nonzero
✗Must buy in whole shares unless brokerage supports fractional ETF trading

Vanguard Total Stock Market ETF (VTI)

2ALowest CostFidelity ZERO Total Market Index Fund (FZROX)

Available only at Fidelity. No minimum investment, no transaction fee.

FZROX is the cheapest index fund in existence at 0.00% — Fidelity absorbs all operating costs as a customer acquisition strategy. The fund tracks Fidelity's proprietary US Total Investable Market Index with near-zero tracking error since its 2018 launch. The only real downside is portability: you cannot transfer shares out of Fidelity without selling.

Pros

✓0.00% expense ratio — truly free to hold
✓Mutual fund structure allows automatic investing in exact dollar amounts
✓No minimum investment

Cons

✗Fidelity-only: selling required if you change brokerages
✗Proprietary index, not CRSP or Russell — minor methodology differences

Fidelity ZERO Total Market Index Fund (FZROX)

What to look for in a total-market index fund

The fund landscape looks identical on the surface — near-zero fees, broad diversification, passive management. The differences live in structure, tax treatment, and where you can hold them.

Expense ratio: every basis point compounds

At a 7% annual return, a 0.09% expense ratio versus 0.00% costs roughly $9,000 on a $100,000 investment over 30 years. That gap narrows the longer you hold, but it never closes. For long-term buy-and-hold investors, the cheapest fund wins by default — assuming equivalent coverage.

ETF vs mutual fund structure

ETFs trade intraday and carry a structural tax advantage: they can shed low-cost-basis shares via in-kind redemptions, avoiding capital gains distributions. Mutual funds distribute gains to all shareholders regardless of whether you sold. Over decades in a taxable account, this structural difference can outweigh a small expense ratio advantage.

Index coverage: total market vs S&P 500

Total market funds (VTI, FZROX, SWTSX, SCHB) hold roughly 3,500–4,000 US stocks including small- and mid-caps. S&P 500 funds (SPY) hold 503 large-caps. Historically the return difference is small — small-cap premium is real but inconsistent — but total market funds give you full US equity exposure without a size bet.

Brokerage portability

ETFs (VTI, SCHB, SPY) transfer freely between brokerages via ACATS. Mutual funds (FZROX, SWTSX) are generally brokerage-specific: FZROX cannot be held outside Fidelity, SWTSX requires Schwab. If you ever change brokerages, you must sell mutual fund shares — a taxable event in non-retirement accounts.

Liquidity and bid-ask spread

SPY is the most-traded ETF on the planet with daily volume exceeding $20 billion and spreads of one cent or less. VTI has $400M+ in daily volume with similarly tight spreads. SCHB trades around $100M daily — more than adequate for individual investors. Bid-ask spread matters only if you trade frequently; buy-and-hold investors can ignore it almost entirely.

How the five funds have performed

VTI, SWTSX, and SCHB have tracked the same CRSP US Total Market Index (or close equivalents) within a few basis points annually for over a decade. Their 10-year annualized returns through 2025 are within 0.05% of each other — effectively identical. FZROX has existed only since 2018 but has tracked its proprietary Fidelity US Total Investable Market Index with near-zero error.

SPY tracks the S&P 500, which has outperformed total market funds in 8 of the last 15 years due to large-cap dominance. Over full market cycles, the difference is negligible — the 2000s saw small-caps outperform significantly. Neither approach has a durable edge; your preference for simplicity or completeness matters more than picking the historically-superior index.

Bottom line

If you want the lowest possible cost and live inside Fidelity's ecosystem, FZROX's 0.00% ER is hard to argue against — just understand you cannot transfer the shares if you leave. VTI is the consensus choice for taxable accounts at any brokerage: ultra-low cost, maximum liquidity, and the ETF structure minimizes capital gains distributions. SCHB is the identical pick for Schwab users who prefer their native fund family.

SWTSX makes sense only inside a Schwab retirement account where portability is irrelevant. SPY belongs in options strategies, institutional portfolios, and short-term tactical trades — its 0.09% ER is a needless drag for long-term buy-and-hold investors who can buy VOO at 0.03% for the same S&P 500 exposure. Match the fund to your brokerage and your time horizon, then stop thinking about it.

Frequently asked questions

Is FZROX really free? What's the catch?▼

FZROX has a 0.00% expense ratio — no hidden fees inside the fund. The catch: it can only be held at Fidelity. If you move to another brokerage, you must sell (a taxable event outside retirement accounts). It also uses Fidelity's proprietary index, not a widely-licensed one like CRSP or Russell.

VTI vs SCHB — which is better for a Schwab user?▼

For a Schwab account holder, SCHB is the natural choice: same 0.03% ER, tracks nearly the same index, auto-invests without currency conversion friction. VTI is marginally more liquid, but for a buy-and-hold investor the practical difference is zero.

Why does SPY have a higher expense ratio than VOO?▼

SPY was created in 1993 under a trust structure that makes it legally difficult to lower fees. State Street's VOO-equivalent (SPY) launched decades before Vanguard's VOO and built its brand among traders who value its liquidity and options market. Long-term investors should use VOO (0.03%) or IVV (0.03%) instead of SPY for S&P 500 exposure.

Can I hold VTI in a Roth IRA?▼

Yes — VTI can be held in any brokerage's Roth IRA, traditional IRA, 401(k) brokerage window, or taxable account. Its ETF structure is especially valuable in taxable accounts where capital gains distributions would otherwise create a tax drag.

Total market fund vs S&P 500 fund — which has better long-term returns?▼

Neither has a durable edge over full market cycles. The S&P 500 outperformed in the 2010s due to large-cap tech dominance; the total market outperformed in the 2000s when small-caps led. The difference in any given 10-year window is typically under 0.5% annualized. Pick total market if you want complete US coverage; pick S&P 500 if you prefer the well-known benchmark.