Nasdaq 100 Index: Companies and Weighting

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The Nasdaq-100 (ticker NDX) tracks 100 of the largest nonfinancial companies listed on the Nasdaq stock market. It uses a modified market-capitalization method: bigger companies count for more, but Nasdaq caps how much any single stock, or a small group of stocks, can dominate the index. Its membership and weights explain most of how the index level moves.

What the Nasdaq-100 Holds

The index excludes banks, insurers and other financial-sector companies. It holds stocks from technology, consumer discretionary, healthcare, telecommunications, industrials, consumer staples, basic materials, utilities and energy. Technology is by far the largest group. In a September 2026 sector breakdown, technology made up roughly two-thirds of the index and consumer discretionary about a sixth. Every other sector was in the low single digits or below 1%.

The Nasdaq-100 is a different index from the Nasdaq Composite. The Composite includes nearly every stock listed on Nasdaq, financials included, which amounts to thousands of companies. When a news report says “the Nasdaq,” it usually means the Composite. NDX is the narrower large-company benchmark.

How Companies Qualify

To be eligible, a security must meet these conditions:

• Exclusive Nasdaq listing. It must be listed only on a Nasdaq exchange. Common stocks, ordinary shares, American depositary receipts (ADRs) and tracking stocks can qualify.
• Nonfinancial. Companies classified in the financial sector are excluded.
• Seasoning. It must have traded on an exchange for at least three months.
• Liquidity. It needs an average daily trading value of at least $5 million over the prior three months.
• No size minimum. There is no fixed market-cap threshold. Eligible companies are ranked by size, and the largest make the cut.

Membership is reset each December at the annual reconstitution. The largest eligible companies enter, and members that have fallen too far down the ranking leave. Every fund tracking the index must then buy a new member’s shares on the effective date.

How the Weighting Works

Each company’s starting weight comes from its market capitalization: share price times shares outstanding. The index level is the sum of those market values divided by a divisor. Nasdaq adjusts the divisor whenever constituents change or corporate actions occur, so that membership changes alone do not move the level.

Pure market-cap weighting would let a handful of giants overwhelm the index. That is why Nasdaq checks the distribution every quarter and adjusts weights when it breaks these limits:

• No single company may exceed 24% of the index.
• Companies weighing more than 4.5% each may not add up to more than 48% combined.

If either limit is breached, the largest weights are scaled down and the excess is spread across the remaining members.

Special Rebalancing

Nasdaq can also rebalance outside the regular schedule. The best-known special rebalance came on July 24, 2023, after a rally in Microsoft, Apple, Nvidia, Amazon and Tesla pushed the combined weight of members above 4.5% past the 48% ceiling. It cut those weights and raised everyone else’s. The index saw a short decline afterward but no noticeable jump in volatility.

Which Companies Carry the Most Weight

Even after the caps, the top of the index is concentrated. In a September 2026 snapshot, the ten largest weights belonged to:

1. Nvidia
2. Apple
3. Microsoft
4. Amazon
5. Alphabet Class A
6. Alphabet Class C
7. Space Exploration Technologies
8. Broadcom
9. Meta
10. Tesla

Alphabet appears twice because each of its share classes is a separate index security. In that snapshot, the top three each weighed roughly 9% to 13%, and the top ten together accounted for more than half of the index. Weights move every trading day with prices, so this ranking can change between rebalances.

Reading the NDX Quote

The headline figure is the index level in points. It is labeled in USD because the constituents trade in dollars, but you cannot buy one unit of NDX for that amount. The change figure compares the latest level with the previous close. The day range shows the session’s low and high. The 52-week range places today’s level within the past year’s span.

NDX is a price-return index, so the dividends constituents pay are not added back. A fund tracking it pays those dividends out to holders, which means a fund’s total return can differ slightly from the index’s percentage change. The performance periods (1D through 1Y) are price changes over each window, not annualized returns.

Because of the concentration described above, a large move in the index can come mostly from a few stocks. Here is a hypothetical example: if stocks making up half the index rise 4% and the rest are flat, the index gains about 2%, even though most members did nothing.

What Moves the Nasdaq-100

• Earnings and guidance from the largest members. Results from a top-five company can shift the whole index.
• Interest rates and inflation expectations. Much of the index’s value rests on expected future earnings growth, so changes in rates and the discount applied to those earnings tend to affect it noticeably.
• Sector sentiment. Shifts in views on technology themes, such as semiconductors or AI spending, flow straight through the heavy tech weighting.
• Index mechanics. Reconstitutions and special rebalances change weights, and funds trade to match them.

The Nasdaq-100 is more concentrated in technology than the S&P 500, which covers about 500 companies including financials. It also differs from the price-weighted Dow Jones Industrial Average. The three can diverge sharply on days when tech leads or lags.

Ways to Get Exposure

You cannot buy the index directly. You can, however, own products that track it:

• ETFs trade like stocks throughout the day.
• Mutual funds are priced once a day.
• Futures and options are leveraged instruments mainly used for hedging and short-term trading.
• Annuities in some cases offer index-linked options.

FAQs

The Bottom Line

Anyone reading the NDX quote or holding a fund that tracks it should know how concentrated the index is. With technology near two-thirds of the weight and the top ten names above half, a few large companies can drive most of a day's move. Interest rates, big-company earnings and rebalances all show up quickly in the index level.