Labcorp Holdings Inc. has moved ahead of STERIS plc in the ranking of the largest U.S. companies. According to market data analyzed by The Online Investor, Labcorp now holds the 357th position by market capitalization within the S&P 500 index. STERIS now sits at 358.
This shift is based on the closing market values for Wednesday, April 22, 2026. Labcorp’s market cap was calculated at $22.53 billion. STERIS was valued at $21.54 billion.
Also read: General Dynamics Stock Falls as S&P 500 Gains
The Mechanics of Market Value
Market capitalization represents the total dollar value of a company’s outstanding shares. It is calculated by multiplying the current stock price by the total number of shares. This metric offers a standardized way to compare companies of different sizes and share prices.
For example, a $20 stock is not inherently worth more than a $10 stock. The share count matters. Market cap factors this in, creating a direct comparison. “Many beginning investors look at one stock trading at $10 and another trading at $20 and mistakenly think the latter company is worth twice as much,” the report from The Online Investor noted. “That is a completely meaningless comparison without knowing how many shares of each company exist.”
Also read: Soybean Futures Drop on Weak Product Prices
Why Ranking Matters for Investors
A company’s size classification, determined by its market cap, directly influences its investor base. Many mutual funds and exchange-traded funds (ETFs) have strict mandates based on company size.
A fund focused on large-cap stocks may only invest in companies valued above $10 billion. Other funds track specific index subsets, like the S&P MidCap 400, which excludes the S&P 500’s 100 largest companies. A shift of just a few ranking spots can determine which funds are eligible to own a stock. This affects trading liquidity and investor demand.
Recent Trading Activity
The ranking change occurred despite opposing price movements for the two stocks on Wednesday. Labcorp shares closed down approximately 0.2%. STERIS shares finished the day up about 1.9%.
This indicates the market cap shift was driven by the underlying share count and the relative scale of each company’s equity. Short-term price swings are less significant than the broader valuation picture for index composition.
Broader Market Context
Both Labcorp and STERIS operate in the healthcare sector. Labcorp is a global life sciences company providing clinical laboratory and drug development services. STERIS is a provider of infection prevention and surgical products and services.
Their movement within the S&P 500 is a minor reshuffling in the index’s lower tiers. But it highlights the constant fluctuation of corporate valuations. The S&P 500 is weighted by market capitalization, making these valuations the core determinant of a company’s influence within the benchmark index.
Data from The Online Investor tracks these rankings daily. The firm provides the underlying analysis for a family of financial news websites.
For investors, the takeaway is clear. A company’s stock price is just one piece of the valuation puzzle. The full picture requires understanding its total market value and how that stacks up against peers.
This article was produced with AI assistance and reviewed by our editorial team for accuracy and quality.
