ILMN vs TMO: Which Is the Better Buy in 2026?
Last updated August 2026
Short answer
ILMN and TMO are similarly sized, but TMO trades noticeably cheaper on forward earnings (20.88x vs 34.57x): the market is paying up for ILMN's profile and pricing TMO more conservatively, or for faster growth. Which you prefer comes down to the drivers you believe, and whether adding either over-concentrates what you already own.
ILMN vs TMO: the tie-breaker metrics
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.
| Metric | ILMN | TMO | What it tells you |
|---|---|---|---|
| Forward P/E | 34.57 | 20.88 | Valuation on next year's expected earnings, the same yardstick for both. Lower is cheaper for that growth; higher means the market is paying up. |
| Trailing P/E | 38.34 | 30.86 | Valuation on the last 12 months. A big drop from trailing to forward means the market expects earnings to jump, so more growth is already in the price. |
| Beta | 1.47 | 0.87 | Volatility vs the market. Above 1 swings harder than the index; below 1 is steadier. Higher beta means bigger drawdowns to hold through. |
| Price vs 52-week range | 99% of range | 67% of range | Where today's price sits between the 52-week low and high. Near the high is momentum with less margin of safety; near the low is out of favor or a discount, depending on why. |
| Price / book | 11.65 | 4.11 | How much you pay over book value. Very high can signal an asset-light, high-return business or a rich price. |
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.
Before you buy: how ILMN and TMO affect your concentration
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. ILMN and TMO 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 ILMN and TMO 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.
What does Illumina (ILMN) do?
Illumina designs, makes, and sells next-generation DNA sequencing systems and the consumables that run on them, serving research, clinical, and applied-genomics customers. Its business follows a razor-and-blades model: instruments such as the high-throughput NovaSeq X, the NextSeq, and the benchtop MiSeq seed an installed base, and the bulk of revenue then comes from recurring sequencing consumables (reagents and flow cells), which historically make up the majority of sales. The company is also pushing into multiomics, proteomics, and clinical diagnostics to expand what its platforms can measure. Illumina is headquartered in San Diego, was founded in 1998, and is led by CEO Jacob Thaysen.
What does Thermo Fisher Scientific (TMO) do?
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.
ILMN vs TMO: how do they differ?
Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.
- ILMN drivers: Installed base and the consumables annuity; The NovaSeq X transition.
- TMO drivers: Bioprocessing and Biologic Drug Manufacturing Tailwind; Recurring Consumables and Reagents Engine.
Which fits which kind of investor
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: Competition is intensifying: Ultima Genomics markets bulk whole-genome sequencing near $80 a genome, Element Biosciences' AVITI undercuts benchtop economics, and PacBio and Oxford Nanopore hold long-read niches, all pressuring Illumina's pricing and share. For TMO, 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.
ILMN or TMO: which should you pick?
ILMN vs TMO: the full fundamentals
ILMN. Illumina trades at a premium earnings multiple that reflects its platform dominance and consumables annuity, set against low-single-digit revenue growth and a slow-growing end market. Full-year 2025 revenue was about $4.34 billion, and the company guided fiscal 2026 to roughly $4.5 to $4.6 billion with operating margins recovering toward the low-to-mid 20s. All figures are approximate, tied to the June 2026 asOf date, and move with the share price and reported results; verify current numbers before relying on them.
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.
Headline figures (approximate, June 2026): ILMN shows revenue (fy2025) ~$4.34 billion (approximate, verify), 2026 revenue guidance ~$4.5-4.6 billion, ~4-6% growth (company guidance, verify), consumables mix Majority of revenue is recurring consumables (razor-and-blades; verify), non-gaap operating margin (2026 guide) ~23.3-23.5% (company guidance, verify); 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%.
The bottom line: ILMN vs TMO
ILMN and TMO 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 ILMN and TMO exposure against your real portfolio. It is not an investment adviser.
Wondering how ILMN or TMO fits the portfolio you already own? Walnut is an AI investing app that connects your brokerage read-only and answers questions like that about your actual holdings: overlap, concentration, and how each position tracks the S&P 500. Compare the best AI portfolio analyzers or see the best AI investing apps in 2026.
Investing in Illumina with AI
Connect the broker you already use and ask Walnut's AI how ILMN fits what you actually hold: whether you own it already through a fund, what it would do to your concentration, and how it has tracked the S&P 500. Read-only by default, and you approve anything before it reaches your broker.
FAQ
What is the difference between ILMN and TMO?
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Illumina designs, makes, and sells next-generation DNA sequencing systems and the consumables that run on them, serving research, clinical, and applied-genomics customers. 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. They show up together because they share investment themes, but they are different businesses, so the better fit depends on which thesis you are expressing.
Is ILMN or TMO the better stock?
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Neither is universally better; they suit different views and risk levels. Walnut is informational, not investment advice. Compare what each does, the tie-breaker metrics above, and the risks, then decide which fits your thesis and what you already own.
Which is cheaper, ILMN or TMO?
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On forward P/E (as of August 2026), ILMN trades at 34.57x and TMO at 20.88x, so TMO is the cheaper of the two on next year's expected earnings. A lower multiple is not automatically the better buy: a richer valuation can be justified by faster growth, and a lower one can reflect real risk. Weigh the multiple against how fast each business is compounding.
Should you own both ILMN and TMO?
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Because they share themes, owning both concentrates you in that theme. That can be intentional (a focused bet) or accidental (less diversification than it looks). Walnut can show your combined exposure across both, and whether adding either over-concentrates you, before you buy.
What are the risks of ILMN vs TMO?
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ILMN: Competition is intensifying: Ultima Genomics markets bulk whole-genome sequencing near $80 a genome, Element Biosciences' AVITI undercuts benchtop economics, and PacBio and Oxford Nanopore hold long-read niches, all pressuring Illumina's pricing and share. The underlying sequencing market is growing slowly, and soft academic and research funding, including pressure on US research budgets, can delay instrument purchases. China is now only about 3% of revenue after Illumina was effectively shut out of that market, where domestic players BGI and MGI dominate. Tariffs and a relatively high valuation add further risk. TMO: 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. Thermo Fisher's active acquisition strategy carries integration and leverage risk, particularly after committing approximately $13 billion to mergers and acquisitions in 2025 alone, and a large deal that underperforms expectations could weigh on earnings and the balance sheet simultaneously. Geopolitical friction, particularly regarding China, creates both a demand risk (softer orders from Chinese academic and industrial customers) and a supply chain risk, while tariff policy changes can disrupt cost structures. Finally, the stock's valuation, though below its own ten-year average on a trailing price-to-earnings basis, still prices in sustained mid-single-digit organic growth, leaving limited room for disappointment if end markets soften.
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Walnut is informational, not investment advice. This page is descriptive and not a recommendation to buy or sell ILMN or TMO; figures are approximate and dated (as of August 2026). Verify current data before investing.