SpaceX completed the biggest market debut on June 12, and major U.S. stock indexes will slot the rocket maker into their baskets within days. Vanguard‑style funds that track the CRSP U.S. Total Market Index plan to add the stock after five trading sessions, meaning millions of retirement accounts will hold a sliver of the company.

Using float‑adjusted weighting, the calculator shows SpaceX would represent roughly 0.1% of a typical U.S. stock index – about $150 per share at the opening price. By contrast, Nvidia, Apple and Microsoft each command 4‑7% of the same fund, while Tesla’s stake is ten times larger than SpaceX’s. The limited public float, roughly 5% of total shares, keeps the exposure modest.

Vanguard’s chief investment officer says even mega IPOs barely move 401(k) balances because index weights are tiny. As insider lock‑ups ease, more shares could trade, potentially nudging the fund weight higher. For now, the addition of SpaceX adds a novelty line item rather than a portfolio driver.