Top ETFs by Market Cap

An Exchange-Traded Fund (ETF) is a type of investment fund that holds a collection of underlying assets — such as stocks, bonds, commodities, or a mix — and trades on a stock exchange just like an individual stock. ETFs offer investors diversified exposure to many assets through a single purchase. They are known for their low costs, tax efficiency, and liquidity compared to traditional mutual funds.

The expense ratio is the annual fee an ETF charges investors, expressed as a percentage of assets under management. For example, an ETF with a 0.03% expense ratio charges $3 per year for every $10,000 invested. Index ETFs tracking broad markets like the S&P 500 tend to have very low expense ratios (often under 0.10%), while actively managed or niche ETFs can charge significantly more.

An ETF's market cap is calculated by multiplying its share price (NAV) by the total shares outstanding — similar to a stock. However, unlike a stock, an ETF's market cap represents the total market value of the fund's shares, not the underlying companies it holds. For broad index ETFs like SPY or QQQ, the fund's market cap reflects assets under management (AUM), which grows as more investors buy shares.

Both ETFs and index funds track a benchmark index, but they differ in how they are traded. Index funds are mutual funds bought and sold at end-of-day NAV prices through a fund company. ETFs trade continuously on stock exchanges throughout the day at market prices that may differ slightly from NAV. ETFs also typically have lower minimum investment requirements and greater tax efficiency due to their in-kind creation/redemption mechanism.

The largest ETFs by market cap are typically broad US equity index funds. SPDR S&P 500 ETF Trust (SPY), iShares Core S&P 500 ETF (IVV), and Vanguard S&P 500 ETF (VOO) consistently rank among the biggest ETFs globally, each holding hundreds of billions in assets. Other large ETFs include those tracking the Nasdaq-100, total stock market, and bond markets.