Best S&P 500 Index Funds to Buy in 2025

What Makes an S&P 500 Index Fund Worth Buying

Picking the best S&P 500 index fund comes down to a few concrete details: expense ratio, tracking error, fund size, and how the fund handles dividends. Because these funds all hold the same roughly 500 large-cap U.S. stocks, the differences between them are small in theory but meaningful in practice over decades of compounding. A fund with a 0.03% fee versus one at 0.10% leaves a noticeable gap in your balance over 20 or 30 years. The same applies to how closely a fund mirrors its benchmark and whether it uses physical replication or synthetic structures.

The best S&P 500 index funds tend to be broad, liquid, and backed by major providers. They suit buy-and-hold investors who want market-level returns without trying to time the stock market. Before comparing specific funds, it helps to understand what you should be looking for.

Key Factors to Compare

Expense Ratio and Fees

The expense ratio is the annual cost of running the fund. For passive S&P 500 funds, this number is usually very low, but even a few basis points matter at scale. Look at the net expense ratio, not the gross figure, and check whether the fund charges a 12b-1 fee or sales load. The best S&P 500 index funds typically charge 0.03% or less per year.

Tracking Error and Replication

Tracking error measures how closely the fund follows its benchmark. A low tracking error means the fund delivers returns very close to the S&P 500 itself. Most top funds use physical replication, meaning they actually own the stocks in the index, which tends to produce tighter tracking than synthetic approaches that use derivatives.

Fund Size and Liquidity

Larger funds generally trade more cheaply and have narrower bid-ask spreads, which matters if you trade frequently or invest through a brokerage with per-trade costs. A fund with deep liquidity also reduces the risk of the provider shutting it down, which can create tax headaches for shareholders.

Dividend Handling

S&P 500 companies pay dividends throughout the year. Some funds distribute them to shareholders, while others reinvest automatically. The best S&P 500 index funds make it clear how dividends are handled and give you the option that matches your needs.

Top S&P 500 Index Funds Compared

What the Table Tells You

The best S&P 500 index funds cluster at the low end of the fee spectrum. Schwab and Fidelity come in below 0.03%, while SPY runs slightly higher at 0.09%. The difference between SPY and the others is small in absolute dollar terms for a long-term buy-and-hold investor, but it adds up if you are comparing multiple funds or reinvesting dividends over many years. All five funds use physical replication, which is the simpler and more transparent approach.

Trade-Offs Between the Best S&P 500 Index Funds

The best S&P 500 index fund for one investor is not always the best for another, and the trade-offs are worth understanding before you commit. The main tension is between cost, convenience, and fund structure.

• VOO vs. IVV: Both charge 0.03% and track the index tightly. Vanguard's fund benefits from the company's investor-friendly structure, while iShares offers deep liquidity across global markets.
• SPY vs. the rest: SPY is the oldest and most liquid S&P 500 ETF, making it the go-to choice for active traders. Its higher expense ratio matters less if you trade infrequently and care most about tight spreads.
• Schwab and Fidelity: These funds often win on raw cost, with expense ratios at or below 0.02%. They are strong choices for investors who already hold other products from the same provider and want a simple, low-cost core holding.

How to Choose the Right Fund for Your Portfolio

The best S&P 500 index fund is the one you will hold consistently. If your brokerage offers commission-free trading on a specific fund, that narrows the decision quickly. If you want the simplest possible choice, the three largest funds — VOO, IVV, and SPY — are broadly interchangeable for long-term investors who do not plan to trade frequently.

Consider where the fund sits within your overall asset allocation. If you already own international or small-cap funds from the same provider, picking the matching S&P 500 fund can reduce friction and keep your portfolio easier to manage. On the other hand, if you are building a portfolio from scratch, let cost and liquidity guide you more than brand loyalty.

One practical detail worth checking is the minimum investment. Most S&P 500 ETFs trade like stocks, so you can buy a single share. Index mutual funds sometimes carry minimums, though many of the best S&P 500 index funds waive them for automatic investments. If you are starting with a small amount, that matters.

What to Expect From an S&P 500 Fund Over Time

S&P 500 index funds deliver the performance of the U.S. large-cap stock market, minus fees. Over long periods, that has been a strong return, but it is not guaranteed. The fund will go through stretches of underperformance relative to other asset classes, and it will not protect you from market downturns. The best S&P 500 index funds do not try to beat the market; they give you efficient, low-cost exposure to it.

If your goal is steady, hands-off wealth building, a single S&P 500 fund can serve as the backbone of a portfolio. Pair it with bonds and international exposure if you want more diversification, or keep it simple if you are comfortable with U.S. large-cap risk. The right fund is the one that matches your time horizon, risk tolerance, and willingness to ignore short-term noise.