As of January 2026 Quest Diagnostics has a market cap of โน1.916 Trillion. This makes Quest Diagnostics the world's 1122th most valuable company by market cap according to our data. The market capitalization, commonly called market cap, is the total market value of a publicly traded company's outstanding shares and is commonly used to measure how much a company is worth.
On Jan 30th, 2026 the market cap of Quest Diagnostics was reported to be: