The scores
Purina ONE SmartBlend: C grade, 58/100
Purina Pro Plan: C grade, 62/100
Both land in the C grade range, but Pro Plan sits 4 points higher. That may not sound like much, but in our scoring system, those points come from genuinely useful ingredient additions that make a real difference in your dog's daily nutrition.
How the ingredients compare
Here are the top five ingredients side by side:
Purina ONE: Chicken, Rice Flour, Corn Protein Meal, Whole Grain Corn, Chicken By-Product Meal
Purina Pro Plan: Chicken, Rice, Poultry By-Product Meal, Soybean Meal, Corn Protein Meal
Both lead with chicken. Pro Plan uses whole rice instead of rice flour — a less processed form of the same grain. Both include by-product meals, though Pro Plan uses the broader "poultry" by-product meal rather than specifying chicken. The carbohydrate strategies differ slightly: Purina ONE doubles down on corn, while Pro Plan introduces soybean meal (a protein-rich legume ingredient, though a common allergen for some dogs).
Where Purina Pro Plan pulls ahead
The real difference isn't in the top five — it's further down the ingredient list. Pro Plan includes chelated (proteinated) minerals, which are bound to amino acids for significantly better absorption than the standard mineral salts found in Purina ONE. This means your dog actually uses more of the zinc, iron, copper, and manganese in the formula rather than passing them through.
Pro Plan also includes live probiotics (guaranteed viable microorganisms), which support digestive health and immune function. These are added after the cooking process to ensure they survive. Purina ONE has chicory root as a prebiotic but lacks actual probiotics.
Rice in Pro Plan is a more whole-food carbohydrate source than Purina ONE's rice flour, retaining more of its natural fiber and nutrients. Shop on Amazon →
Where Purina ONE holds its own
Purina ONE costs noticeably less per pound — typically $3–5 less per bag. For a healthy adult dog with no special dietary needs, it covers the nutritional basics adequately. The chicory root prebiotic is a legitimate functional ingredient, and the overall vitamin and mineral panel is comprehensive even without the chelated forms.
Purina ONE also avoids soybean meal, which is present in Pro Plan. While soy is safe for most dogs, it is one of the more common allergens. If your dog has soy sensitivity, Purina ONE might actually be the better choice between these two. Shop on Amazon →
The bottom line
Purina Pro Plan (C/62) edges out Purina ONE (C/58) with chelated minerals and live probiotics that justify the modest price increase. If you're already buying Purina ONE and can afford a few extra dollars per bag, stepping up to Pro Plan is one of the easiest and most worthwhile upgrades in the budget dog food space.
That said, both are still C-grade foods. If you're looking for a bigger jump in quality, Diamond Naturals (B/78) or Kirkland Signature (B/78) offer B-grade nutrition at prices that often compete with Pro Plan.