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Brand Comparison · 2026

Hill's Science Diet vs Kirkland Signature

Hill's Science Diet (veterinarian-recommended premium kibble with the deepest prescription-diet portfolio on the market) and Kirkland Signature (Costco's private-label dry food, reportedly made by Diamond Pet Foods, which meets 2 of WSAVA's 5 questions) compared head-to-head on WSAVA manufacturer-quality criteria, AAFCO substantiation, monthly cost, and which dog each is best for in 2026. Hill's Science Diet meets 5 of 5 WSAVA criteria. Kirkland Signature is roughly 71% less than Hill's Science Diet.

The verdict

At about $20 a month, Kirkland Signature costs $35 to $65 less than Hill's Science Diet at $55-85. The evidence gap runs the other way. Hill's meets all 5 WSAVA questions, with AAFCO feeding tests and 50+ years of trial data from its own research facility. Kirkland Signature meets 2 of 5. Its label says "formulated to meet" AAFCO profiles, Costco's page names no manufacturer, though Costco's 2025 pet FAQ said Diamond Pet Foods makes the dry foods.

Hill's suits owners who want a brand with a clinical record and a route to Prescription Diet later. Kirkland Signature suits Costco members who put cost first and accept a thinner paper trail. For a dog with a known condition, the veterinarian chooses the food, and the price gap should not enter into it.

Key differences at a glance

Quick comparison

DimensionHill's Science DietKirkland Signature
Parent companyColgate-PalmoliveCostco (reportedly made by Diamond Pet Foods)
CategoryPremium dry kibbleMass-market dry kibble
WSAVA criteria met5 of 52 of 5
AAFCO substantiationFeeding trialsFormulation only
Full-time veterinary nutritionistYesPartial
Credentialed formulatorYesPartial
AAFCO feeding trialsYesNo
Owns manufacturing plantsYesYes
Quality control programYesYes
Typical monthly cost (50 lb dog)$55 – $85 / month$20 / month

Colgate-Palmolive

Hill's Science Diet

Veterinarian-recommended premium kibble with the deepest prescription-diet portfolio on the market.

Strengths

  • Most extensively used brand in US veterinary clinical practice
  • 50+ years of feeding trial data from an owned research facility
  • Strong palatability across life stages
  • Pairs cleanly with Hill's Prescription Diet for any future therapeutic needs

Watch-outs

  • Higher price than Purina Pro Plan at comparable nutritional spec
  • Less breed-specific formulation than Royal Canin
  • Vitamin D toxicity recall in 2019 affected canned formulas

Best for: Healthy adult dogs where you want continuity from over-the-counter to prescription within a single brand.

Avoid if: You are highly price-sensitive and your dog has no medical conditions.

Visit Hill's Science Diet ↗

Costco (reportedly made by Diamond Pet Foods)

Kirkland Signature

Costco's private-label dry food, reportedly made by Diamond Pet Foods, which meets 2 of WSAVA's 5 questions.

Strengths

  • Low price, about $1 a pound for the 25 lb bag, or roughly $20 a month for a 50 lb dog
  • Diamond, the reported maker, publishes a test-and-hold program with certified-lab testing
  • Diamond operates seven US manufacturing facilities and is family-owned

Watch-outs

  • Costco's product page names no manufacturer. Costco's 2025 pet FAQ said Diamond makes the dry foods, but the bag's own maker line was not checked
  • Label says "formulated to meet" AAFCO profiles rather than citing feeding trials
  • No named nutritionist or formulator. Diamond describes only unnamed experts
  • Costco's Nature's Domain grain-free line was named in 29 reports in the FDA's 2019 DCM update. The FDA did not establish that any food caused the disease

Best for: Costco members who want a low-cost dry food and will check the bag's manufacturer line themselves.

Avoid if: You want a named, credentialed nutrition team or feeding-trial substantiation behind the food.

Visit Kirkland Signature ↗

Which is better for your dog?

The right pick depends on your individual dog. Hill's Science Diet is the better choice when: Healthy adult dogs where you want continuity from over-the-counter to prescription within a single brand. Kirkland Signature is the better choice when: Costco members who want a low-cost dry food and will check the bag's manufacturer line themselves.

On cost, Kirkland Signature is roughly 71% less than Hill's Science Diet at the midpoint of typical premium spec for a 50 lb adult dog. On WSAVA manufacturer-quality criteria, Hill's Science Diet meets 5 of 5 vs 2 of 5 for Kirkland Signature.

Checking one brand rather than the pair? See is Hill's Science Diet WSAVA-approved or is Kirkland Signature WSAVA-approved.

Where to buy

Made your pick?

Check current pricing on whichever brand fits your dog. Prices and promotions change frequently, so it is worth comparing both before you commit to a bag or a subscription.

Shop Hill's Science Diet on Chewy →

Disclosure: these are affiliate links and IntelliBowl may earn a commission at no extra cost to you. Commission does not influence the comparison above. See our methodology.

Personalized recommendation

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Compare these brands against others

Methodology: WSAVA criteria reflect each brand's publicly documented manufacturer-quality practices as of October 2026, scored against the WSAVA Global Nutrition Committee's 5-question rubric. AAFCO substantiation reflects the dominant method used across the brand's main retail product line. Monthly cost reflects typical US 2026 retail for a 50 lb adult dog at premium spec, before autoship discounts. Recommendations are editorial and not influenced by affiliate relationships. See our recommendation methodology for IntelliBowl's quiz-engine ranking logic.