Pet Food Comparison: How to Compare Pet Food: What the Labels Don’t Tell You

Around 40% of dog and cat owners switched their pet’s food at least twice in the past year. Most picked the replacement by reading a star rating or the front of a bag. Almost none of them ran the one calculation that actually reveals nutritional quality — and most comparison sites don’t run it either.

The Dry Matter Calculation: The Only Number That Lets You Compare Foods Honestly

The guaranteed analysis panel on every bag or can shows crude protein, crude fat, crude fiber, and moisture. Most owners look at the protein percentage and stop there. That is where the comparison falls apart.

A dry kibble showing 28% protein and a wet food showing 9% protein look completely different. On a dry matter basis — once you strip out the moisture — they can be nearly identical. Wet food typically runs 75–80% moisture; dry kibble sits at around 10%. Without accounting for that gap, you are comparing apples to water.

Here is the calculation: divide the nutrient percentage by (100 minus the moisture percentage), then multiply by 100.

Purina Pro Plan Classic Adult Chicken wet food lists 9% protein at 78% moisture. Dry matter protein = 9 ÷ 22 × 100 = 40.9%. Compare that to Purina Pro Plan Savor Adult dry at 26% protein and 12% moisture: dry matter = 26 ÷ 88 × 100 = 29.5%. The wet food has significantly more usable protein per gram of actual food substance. That single fact reverses how most owners think about wet versus dry nutrition.

Where to Find the Moisture Content

It is listed in the guaranteed analysis panel on every label. Royal Canin, Hills Science Diet, Orijen, and Purina all publish complete guaranteed analysis data publicly on their websites. If a brand does not list moisture content, that is worth noting before you buy.

What the AAFCO Statement Actually Means

Below the guaranteed analysis, look for the AAFCO nutritional adequacy statement. “Formulated to meet the nutritional levels established by AAFCO” means the recipe was calculated on paper. “Substantiated by AAFCO feeding tests” means actual animals ate the food and were measured for health outcomes over time. Purina Pro Plan and Hills Science Diet use feeding trials for key products in their ranges. Most budget brands use the formulation method only.

Dry vs. Wet vs. Raw: A Direct Comparison

The format of food affects cost, nutrition, and risk in ways a star rating cannot capture. Here is the honest side-by-side:

Commercial raw brands like Natures Menu and Benyfit Natural are better regulated than DIY raw, but neither eliminates bacterial contamination risk completely. If young children or immunocompromised people live in your home, that risk profile matters. My recommendation for most households: Orijen or Purina Pro Plan dry paired with wet food rotation hits the best balance of nutrition, cost, and practical safety.

Reading the Ingredient List Without Getting Fooled

The ingredient list is ranked by weight before cooking. This is where marketing does its best work.

• Chicken vs. chicken meal: Fresh chicken is roughly 70% water. After cooking it shrinks dramatically. Chicken meal is already dehydrated — 1kg of chicken meal contains far more actual protein than 1kg of fresh chicken listed first. A bag leading with chicken meal may genuinely outperform one leading with “fresh chicken.”
• Ingredient splitting: If a label lists “maize,” “maize flour,” and “maize gluten” separately, the manufacturer is splitting one ingredient across three entries to push each one lower in the ranking. Combined, corn might outweigh the protein source entirely.
• By-products are not automatically bad: Chicken by-product meal from a named species in a quality facility is nutritionally dense and a legitimate protein source. “Meat and bone meal” from unnamed species is a different matter.
• Preservatives to avoid: Ethoxyquin, BHA, and BHT. Mixed tocopherols (vitamin E) and rosemary extract are the natural alternatives used by better brands.

The Grain-Free Myth

Grain-free foods surged in popularity based on marketing, not veterinary consensus. The FDA investigated a potential link between grain-free diets and dilated cardiomyopathy (DCM) in dogs — research that remains ongoing and inconclusive. For most dogs, whole grains like brown rice and oats are nutritionally sound. Only dogs with a confirmed grain sensitivity need a grain-free formula, and that diagnosis should come from a vet, not a packaging claim.

Five Brands Worth Comparing Right Now

Purina Pro Plan is the brand most vets recommend unprompted. More than 500 published studies reference it. The Sensitive Skin and Stomach Salmon formula (approximately £52 for 14kg) is the strongest specific pick for dogs with digestive issues. Not glamorous, but the evidence base is hard to match.

Orijen Original costs around £70 for 11.4kg and uses 85% animal ingredients, regionally sourced. It is the closest kibble equivalent to a raw-adjacent diet without the handling risk. For most healthy adult dogs the real-world difference over Purina Pro Plan is smaller than the price gap suggests — but for owners who want the highest-end dry food available, it is the honest answer.

Wellness Core Ocean (salmon, whitefish, herring) sits around £45 for 10kg and consistently performs well for skin and coat health. Solid mid-market option with no artificial preservatives.

Hills Science Diet earns its reputation primarily through its prescription ranges — c/d for urinary issues, z/d for food allergies, k/d for kidney disease. The evidence behind those specific formulas is strong. The standard adult range is competent but not exceptional value per gram of protein compared to Wellness Core or Pro Plan.

Blue Buffalo markets aggressively as premium but has faced documented quality control issues and a class action lawsuit over ingredient misrepresentation. At the same price point, I would pick Wellness Core or Purina Pro Plan without hesitation.

Three Mistakes That Send Owners Down the Wrong Rabbit Hole

1. Comparing price per bag instead of per serving. A 15kg bag of Purina Pro Plan costs more than a 15kg bag of a supermarket brand. But if the daily recommended portion is 200g versus 350g because nutrient density differs, the cheaper bag costs more per actual day of feeding. Always calculate cost per 100g, then multiply by your dog’s daily intake in grams.
2. Switching food too fast. Most vets advise 6–8 weeks on a new food before you can fairly evaluate coat condition, stool quality, and energy. Owners who switch every three weeks never gather usable data. They cycle through marketing claims without a real signal from the animal.
3. Treating star ratings as a final answer. Dog Food Advisor and All About Dog Food use ingredient-quality algorithms, not laboratory analysis. A brand can list premium ingredients and source lower-quality versions of those same ingredients. Cross-reference any comparison score with AAFCO feeding trial status and the brand’s published guaranteed analysis before committing.

When the Higher-Rated Food Is the Wrong Choice

A 5-star food on a comparison site can be medically wrong for your specific animal. A dog with kidney disease needs restricted phosphorus — which points directly to Hills k/d or Royal Canin Renal, not whatever leads the general ingredient-quality rankings. The sites rate against a generic healthy adult standard. Never override a vet’s dietary recommendation with a comparison algorithm score.

How to Run a Meaningful Comparison at Home

What should I track when trialing a new food?

Four things: stool consistency and frequency (the most reliable real-world indicator of digestibility), coat condition at four weeks and again at eight weeks, whether your pet finishes meals reliably, and energy levels during the second month on the food. A simple notes app is enough. You do not need anything more structured than dated observations.

How long before I can judge whether it is working?

Coat improvement takes 8–12 weeks for meaningful change. Digestive changes are faster — typically 2–3 weeks. Loose stools during the first two weeks of transition are common and not necessarily a sign of a bad match. Loose stools at week four are a different signal: the food is likely not a good fit for that animal, regardless of what the label says.

Can comparison sites account for my specific pet?

No. All About Dog Food, Dog Food Advisor, and similar tools rate foods against a generic healthy adult standard. A senior large-breed dog needs specific calcium-to-phosphorus ratios, restricted sodium, and ideally added glucosamine — none of which a general 5-star rating reflects. Use comparison sites to build a shortlist of 3–4 candidates, then filter that shortlist against your vet’s specific guidance for your animal’s age, breed, and health status.

Most owners who spend hours on comparison sites land in roughly the same place: a mid-to-premium dry food with some wet food rotation added for hydration and variety. That outcome is broadly supported by nutritional research. And your pet’s stool quality and coat condition over 8 weeks will give you more honest feedback than any website — which is exactly what most comparison sites cannot measure.