How Eight Stocks Move the S&P 500: Weights on 19 October
On 19 October 2026 the eight largest companies in SPY made up 37.1% of the fund. A 1% move in Nvidia alone was worth about 6 S&P 500 points. Here is how to turn a weight into index points and into dollars on an E-mini contract.
By PYE Markets • Published 2026-10-18 • Updated 2026-10-21 • 5 min read
Update, 2026-10-21: Rewritten on 21 October 2026. Weights now come from one dated source, State Street’s SPY holdings file for 19 October 2026, and the worked example uses that day’s S&P 500 close. We removed the Nasdaq-100 weights because we could not get a dated issuer figure for them.
Key points
- In State Street’s SPY holdings for 19 October 2026, the eight largest companies (counting Alphabet’s two share classes as one) made up 37.1% of the fund. The seven companies usually called the “Magnificent 7” made up 34.7%.
- A stock’s effect on the index is roughly its weight times its own move. With the S&P 500 at 7,690.73 (close, 19 October), a 1% move in Nvidia (7.9%) was worth about 6 index points.
- If Nvidia, Apple and Microsoft (21.5% together) all rose 2%, the index would gain about 33 points, or about $1,650 on one E-mini S&P 500 contract.
- Top 8 companies in SPY: 37.1% (19 Oct 2026)
- Largest weight: NVIDIA 7.9% (19 Oct 2026)
- S&P 500 close: 7,690.73 (19 Oct 2026)
The S&P 500 weights each company by its float-adjusted market value, so the largest companies move it most. On 19 October 2026 eight companies made up more than a third of SPY, the largest fund that tracks the index. This piece shows how to work out what a move in one of them means for the index and for an E-mini futures contract.
The arithmetic
A stock’s contribution to the index, in percent, is about its weight times its own percentage change. To turn that into index points, multiply by the index level. To turn points into dollars, multiply by the contract’s value per point: $50 for the E-mini S&P 500 (ES) and $5 for the Micro E-mini (MES).
- Worked example: Nvidia’s weight was 7.93% on 19 October. A 1% move × 7.93% = 0.079% of the index. At the 19 October close of 7,690.73, that is about 6.1 points, or about $305 on one ES contract.
- Three stocks together: Nvidia, Apple and Microsoft were 21.46% of SPY. A 2% rise in all three adds about 0.43% to the index, or about 33 points: roughly $1,650 on one ES contract and $165 on one MES.
Broad move or narrow move?
Because a few companies carry so much weight, the index can rise while most of its members fall. One way to see which is happening is to compare SPY, which weights by size, with RSP, which holds the same companies in equal amounts. If SPY rises and RSP does not, the gain is coming from the largest stocks. This describes the market; it is not a trading signal.
What about the Nasdaq-100?
The Nasdaq-100 is even more concentrated, and its rules cap the largest weights at rebalances. We have left out Nasdaq-100 weights here because we could not get a dated figure from the fund issuer or the index provider. The arithmetic above works the same way for NQ, which is worth $20 per index point.
Weights change every day
The figures here are for 19 October 2026 and move with share prices. State Street publishes SPY’s holdings every trading day, so the latest weights are one download away.
Largest companies in SPY, 19 October 2026 (State Street holdings file)
| Company | Ticker | Weight in SPY | A 1% move in the stock, in S&P 500 points (at 7,690.73) |
|---|---|---|---|
| NVIDIA | NVDA | 7.93% | ≈6.1 |
| Apple | AAPL | 7.55% | ≈5.8 |
| Microsoft | MSFT | 5.98% | ≈4.6 |
| Alphabet (both share classes) | GOOGL + GOOG | 5.49% | ≈4.2 |
| Amazon | AMZN | 3.89% | ≈3.0 |
| Broadcom | AVGO | 2.40% | ≈1.8 |
| Meta Platforms | META | 2.35% | ≈1.8 |
| Tesla | TSLA | 1.57% | ≈1.2 |
Eight companies were 37.1% of SPY on 19 October 2026. Weight × move × index level gives the points; points × $50 gives the dollars on one E-mini contract.
Sources
- State Street Global Advisors: SPY daily holdings (as of 19 Oct 2026)
- CME Group: E-mini S&P 500 contract specifications
Weights: SPY holdings file published by State Street Global Advisors, as of 19 October 2026 (fund weights, used as a stand-in for S&P 500 index weights). S&P 500 close: Yahoo Finance daily close, 19 October 2026. E-mini S&P 500 contract value: CME Group ($50 per index point; Micro E-mini $5). General market information, not investment advice.