🥫 Cat Food Carb Calculator
Cat food labels are required to list protein, fat, fibre and moisture — but never carbs. Yet carbs are the difference between a food built for an obligate carnivore and one padded with starch. Copy five numbers off the label; this calculator works out the carbohydrate percentage the label leaves out, on a dry-matter basis so wet and dry foods compare fairly.
The label numbers
Copy them from the Guaranteed Analysis panel on the bag or tin. Percentages only — no weighing, no maths.
Blank ash uses a typical estimate: 6.5% for dry food, 2.5% for wet.
The hidden number
Full dry-matter profile — the fair comparison
| Nutrient | As-fed | Dry matter |
|---|---|---|
| Protein | – | – |
| Fat | – | – |
| Fibre | – | – |
| Carbohydrate (NFE) | – | – |
How it's worked out: carbs = 100 − (protein + fat + fibre + moisture + ash) — the standard "nitrogen-free extract by difference" method. Dry matter removes the water so a 78%-moisture tin and a 10%-moisture kibble compare honestly. Calories use the modified Atwater factors for pet food (protein 3.5, fat 8.5, carbs 3.5 kcal/g). Label values are guaranteed minimums/maximums, so treat the result as a close estimate, not a lab analysis.
Feeding a cat, not just reading about one? Pair this with the Calorie & Feeding Calculator to turn percentages into daily grams.
Why check the carbs in cat food?
🦁 Cats are obligate carnivores
A cat's metabolism is built for protein and fat. Unlike dogs, cats have no dietary requirement for carbohydrate at all — every carb percent in the bowl is there for manufacturing convenience or cost, not for the cat.
🔍 Labels hide it on purpose (sort of)
Regulations require protein, fat, fibre and moisture on the label — carbs simply aren't on the list. Two foods that look identical on the panel can differ by 30 points of starch. This calculator closes that gap in ten seconds.
⚖️ Wet vs dry, honestly compared
A wet food at "10% protein" often beats a dry food at "30%" once the water is removed. Dry-matter numbers are how nutritionists compare foods — now they're how you can, too.
Questions, answered
What carb level should I aim for?
There's no official requirement — cats need 0% carbs nutritionally. As a practical guide, foods under ~10% carbs on a dry-matter basis resemble what a cat's prey-based diet provides; most wet foods land between 5–20%, and dry kibbles typically run 25–50% because starch is what holds a kibble together. Lower isn't automatically better in every case — the whole nutritional picture matters, and your vet knows your cat.
Why is my ash value an estimate?
Ash (the mineral residue) is part of the carb-by-difference equation, but many labels don't print it. Typical values run about 5–8% in dry food and 2–3% in wet food. Using the estimate shifts the carb result by a point or two at most — if your label does list ash, type it in for the tightest number.
Can I use this for dog food?
The arithmetic is identical, but the verdict bands are written for cats. Dogs use carbs far more readily, so a "high" feline reading is unremarkable for a dog food.
Does a high carb % mean the food is bad?
Not by itself — it's one lens. Protein quality, moisture, your cat's weight and health all count. Think of the carb number as spotting the difference between "meat with some starch" and "starch with some meat" — then talk to your veterinarian if you're changing diets for a health reason.
This calculator gives an estimate from label guarantees, for general information only. It is not veterinary or nutritional advice for your individual cat — for diet changes tied to weight or health, talk to your veterinarian.