The scores
Hill's Science Diet Indoor Cat: C (63/100)
Royal Canin Indoor Cat: C (58/100)
A 5-point gap within the same C tier. Hill's lands in the mid-C range on the strength of whole chicken as the first ingredient and a prebiotic (FOS) addition. Royal Canin's 2026 reformulation lifted it out of the D tier by dropping "by-product" from the lead ingredient and adding egg product, FOS, and pea fiber. Both brands now command premium prices for mid-C ingredient quality — Hill's narrowly delivers more per dollar.
How the ingredients compare
Here are the first five ingredients side by side:
Hill's Science Diet: Chicken, Whole Grain Wheat, Corn Protein Meal, Powdered Cellulose, Chicken Fat
Royal Canin: Chicken Meal, Corn, Brewers Rice, Corn Gluten Meal, Wheat
Hill's starts with whole chicken — a named fresh meat with moisture and intact nutrients. Royal Canin now starts with chicken meal, a concentrated rendered protein that's a meaningful upgrade from its previous chicken by-product meal but still a step below whole meat. Hill's second and third ingredients are whole grain wheat and corn protein meal; Royal Canin's are corn and brewers rice. The middle of both lists is grain-heavy, but Hill's trades one of those grain slots for chicken fat (a named animal fat), which narrowly edges it ahead.
Where Hill's Science Diet pulls ahead
Whole chicken first. Hill's leads with whole chicken — a named fresh meat with moisture and intact nutrients. Royal Canin leads with chicken meal, which is a concentrated rendered protein. Both are legitimate animal-protein sources, but for an obligate carnivore a whole meat delivers broader nutrient content and signals that the manufacturer is sourcing from primary ingredients rather than optimizing exclusively for rendered protein density.
Chicken fat in top five. Hill's fifth ingredient is chicken fat — a named animal fat providing essential fatty acids. Royal Canin's fifth ingredient is wheat — a plain grain. The animal-fat inclusion in the top five is a consistent B-tier marker; grain in that slot is a C-tier marker.
Similar grain load, but Hill's grain profile is cleaner. Both brands use grain fillers — Hill's pairs whole grain wheat with corn protein meal, while Royal Canin stacks corn, brewers rice, corn gluten meal, and wheat in its top seven. Whole grain wheat retains more of its bran and germ than brewers rice (a milling by-product) or straight corn, so Hill's grain choices are marginally better for digestion.
Lower price. Hill's Science Diet typically costs less than Royal Canin per pound. Getting better ingredients for less money makes the choice even more straightforward. Shop on Amazon →
Where Royal Canin holds its own
Breed-specific and condition-specific formulas. Royal Canin offers an unusually wide range of specialized formulas — breed-specific, weight management, urinary health, digestive care, and more. If your vet has recommended a very specific Royal Canin therapeutic formula for a diagnosed condition, that recommendation may override general ingredient quality comparisons.
Feeding trial research. Royal Canin invests significantly in feeding trials and has decades of nutritional research behind their formulas. Their approach is more clinical than ingredient-focused, and some veterinary nutritionists value this methodology highly.
Palatability. Royal Canin consistently ranks high in taste-test studies. Their kibble shape and coating are specifically engineered for palatability. If you have a picky cat that refuses other foods, Royal Canin may be one of the few brands they'll eat. Shop on Amazon →
The bottom line
Hill's Science Diet is still the better choice between these two, scoring 5 points higher (C/63 vs C/58) with a slightly stronger ingredient list. Whole chicken first and chicken fat in the top five give Hill's the narrow edge; Royal Canin's 2026 reformulation closed most of the prior 15-point gap but kept it just behind. Both brands lean heavily on vet recommendations and clinic partnerships for their reputation, and when you compare what's actually in the bag, Hill's delivers more for less money. That said, neither brand is truly impressive from an ingredient quality standpoint — both still rely on corn and wheat fillers that cats don't need. If you're willing to spend at this price point, foods like Blue Buffalo (B/78) offer meaningfully better ingredients.
Read our full reviews of Hill's Science Diet and Royal Canin for the complete ingredient breakdowns.