TMO vs WAT: Which Is the Better Buy in 2026?

Same yardstick, side by side (as of August 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.

Reading it: TMO is the cheaper of the two on forward earnings, but cheaper is not the same as better. Pair the valuation with growth (how far the forward P/E sits below the trailing P/E) and risk (beta) before you decide.

The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. TMO and WAT share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.

This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined TMO and WAT exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.

Thermo Fisher Scientific, headquartered in Waltham, Massachusetts, is a global provider of scientific instruments, consumables, reagents, and services used across pharmaceutical and biotech drug development, clinical diagnostics, academic research, and environmental and industrial testing. The company operates through four reportable segments: Life Sciences Solutions (reagents, proteins, and consumables for research and bioproduction), Analytical Instruments (mass spectrometers, chromatography systems, electron microscopes, and laboratory equipment), Specialty Diagnostics (clinical diagnostic kits and transplant diagnostics), and Laboratory Products and Biopharma Services (supply-chain distribution, contract research through PPD, and contract drug manufacturing through Patheon). Revenue is generated through instrument sales, high-margin consumables and reagents that customers repurchase continuously, long-term service contracts, and growing contract development and manufacturing (CDMO) fees; consumables and services collectively account for a majority of annual sales and provide durable recurring revenue.

Full TMO guide

Waters Corporation, based in Milford, Massachusetts, builds the instruments that regulated laboratories use to find out what is in a sample and how much of it. The core lines are liquid chromatography (the ACQUITY and Alliance iS systems), mass spectrometry (Xevo and SYNAPT), thermal analysis and rheometry under the TA Instruments brand, and Empower, the chromatography data software that most pharmaceutical quality-control labs run their methods on. Legacy end markets skew heavily toward pharma and biopharma at roughly ~58% of sales, with industrial and applied testing near ~31% and academic and government customers around ~11%. The February 2026 combination with BD's Biosciences and Diagnostic Solutions business bolted on flow cytometry and reagents plus clinical microbiology and specimen management, adding roughly ~$3B of annual revenue and pushing Waters into diagnostics for the first time.

Full WAT guide

Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.

• TMO drivers: Bioprocessing and Biologic Drug Manufacturing Tailwind; Recurring Consumables and Reagents Engine.
• WAT drivers: The BD combination closed, and Waters kept the ticker; Recurring revenue is the real engine.

A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: The most significant near-term risk is a contraction in research funding from government agencies (including NIH) and from biotech companies whose access to capital markets has historically been cyclical; when funding tightens, customers delay instrument purchases and reduce consumable orders, pressuring organic revenue growth. For WAT, integration risk is the dominant one, because the acquired revenue is close to the size of legacy Waters and diagnostics is a category this management team has not run before.

Pick TMO if you believe its drivers more; WAT if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the TMO and WAT guides.

TMO. Thermo Fisher's trailing price-to-earnings ratio of roughly 26x sits approximately 18% below its own ten-year historical average of about 32x, reflecting a period of softer organic growth as the post-pandemic diagnostics and COVID-related revenue tailwind has faded. The adjusted operating margin of 22.7% for 2025 and management guidance for 6 to 8 percent adjusted EPS growth in 2026 suggest the earnings recovery is progressing, though the pace of organic revenue acceleration remains a key variable the market is watching. Free cash flow of roughly $6.3 billion gives the company significant flexibility for continued share repurchases, dividends, and acquisitions.

WAT. The trailing revenue figure straddles pre-deal and post-deal quarters, so it materially understates the current run rate; the ~$6.4B full-year guide is the cleaner read on the combined company. Waters reports adjusted EPS that excludes purchase accounting and integration charges, and the gap between adjusted and GAAP earnings will stay wide while the BD amortization runs. Analyst price targets in August 2026 clustered near ~$420, close to where the stock traded, with a wide dispersion from roughly ~$330 to ~$480 that captures how differently analysts handicap the integration.

Headline figures (approximate, 2026-06-27): TMO shows revenue (full year 2025) ~$44.6 billion, revenue guidance (full year 2026) ~$46.3 to $47.2 billion, adjusted operating income (full year 2025) ~$10.1 billion, adjusted operating margin (full year 2025) ~22.7%; WAT shows revenue (ttm) ~$4.64B, fy2026 revenue guidance ~$6.42B to ~$6.48B, q2 2026 adjusted eps ~$3.05, fy2026 adjusted eps guidance ~$14.45 to ~$14.65.

TMO and WAT are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined TMO and WAT exposure against your real portfolio. It is not an investment adviser.