COST vs UNH: Which Is the Better Buy in 2026?

Same yardstick, side by side (as of October 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: UNH 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. COST and UNH 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 COST and UNH 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.

Costco Wholesale operates a membership-based warehouse club chain. Members pay an annual fee (currently $65 for basic Gold Star, $130 for Executive) for access to Costco warehouses, where they can buy products at lower markups than traditional retailers. Costco operates approximately 900 warehouses globally, with the largest concentration in the United States plus meaningful presence in Canada, Mexico, the UK, Japan, South Korea, Taiwan, Australia, and other markets.

Full COST guide

UnitedHealth Group is the largest US health insurer and one of the largest healthcare companies in the world. It runs through two main engines. UnitedHealthcare is the insurance arm, providing employer, individual, Medicare Advantage, and Medicaid health plans to tens of millions of members. Optum is the faster-growing health-services arm: Optum Health (physician groups and care delivery, including value-based care), Optum Insight (healthcare data, analytics, and technology), and Optum Rx (one of the largest pharmacy benefit managers in the country). The combination lets UnitedHealth manage both the financing and the delivery of care, capturing margin across the system and using vast claims data to manage costs. Headquartered in Minnetonka, Minnesota, UnitedHealth is a Dow component and one of the largest companies in the S&P 500 by revenue. Its scale, vertical integration, and Medicare Advantage leadership define its competitive position.

Full UNH guide

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

• COST drivers: Membership fee growth; International expansion.
• UNH drivers: Optum growth engine; Medicare Advantage scale.

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: Costco's premium valuation (about 48x trailing and 40x forward earnings in October 2026) embeds high expectations for continued same-store sales growth and margin expansion. For UNH, unitedHealth faces a difficult medical-cost environment: rising utilization (especially in Medicare Advantage) can spike the medical loss ratio and compress margins, as the company has experienced.

Pick COST if you believe its drivers more; UNH 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 COST and UNH guides.

COST. Costco trades at one of the highest P/E ratios in retail, about 48x trailing earnings in mid-October 2026, on the strength of the durable membership model, consistent same-store sales growth (comparable sales up 11.4% in September), and the long runway for international expansion. The multiple has eased from earlier peaks as earnings grew faster than the share price. Analysts rate it a buy with an average target near $1,066, and the valuation has compressed historically only during severe market drawdowns.

UNH. The trailing P/E of about 26x is inflated by the near-zero fourth quarter of 2025; on forward earnings UNH trades near 17x, closer to its historical range. Revenue is enormous but insurance margins are thin, so the valuation hinges on whether the medical cost trend keeps stabilizing and the raised 2026 outlook holds. The stock has recovered a large part of its 2025 decline, which leaves less of a discount for regulatory and cost risk than a year ago.

Headline figures (approximate, October 2026): COST shows revenue (fy2026) ~$303 billion, up ~10% YoY; Q4 up ~11% YoY, operating margin ~3.8% (low, by design; membership fees are the profit lever), net income (fy2026) ~$9.2 billion, eps (fy2026) ~$20.76; Q4 $6.75 vs ~$6.53 consensus; UNH shows revenue (ttm) ~$450 billion; Q3 2026 ~$112.7 billion, ~flat year on year, operating margin ~5.8% (net margin ~3.5%), net income (ttm) ~$15.9 billion (sensitive to medical costs), eps ~$15.55 trailing; Q3 2026 $4.69 vs $4.14 consensus.

COST and UNH 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 COST and UNH exposure against your real portfolio. It is not an investment adviser.