Pet Food Portion Calculator
How it works
Weight first sets a baseline energy need, the Resting Energy Requirement: RER = 70 × weight(kg)^0.75. That is then scaled up by an activity multiplier — low, moderate or high — to reach an estimated daily calorie need, and the calorie need is divided by the food's own energy density (kcal per cup, printed on most bags) to reach a daily amount in cups.
The activity multipliers differ by species: 1.2 / 1.6 / 2.0 for a dog at low / moderate / high activity, versus 1.0 / 1.2 / 1.4 for a cat — commonly cited veterinary ranges reflecting that cats generally need less scaling at the same activity label than dogs do.
This is a starting estimate, not a feeding instruction. Check the food's own feeding chart, and a vet's guidance always takes priority — especially for puppies and kittens, pregnant or nursing animals, or any medical condition.
Frequently asked questions
What is RER, and where does the formula come from?
Resting Energy Requirement — a standard veterinary starting point for estimating a pet's baseline energy need from body weight alone. It uses a well-established "metabolic body weight" scaling relationship (weight raised to the 0.75 power), not a number specific to any one diet or brand, which is why it is only ever a starting point rather than a finished feeding amount.
Why do dogs and cats use different activity multipliers for the same label?
Because they are not the same animal doing the same thing. At the same "moderate" label, a documented cat's activity-driven energy need scales up far less than a dog's — cats are typically far less active even at their own species' high end — so this tool keeps two separate multiplier ranges rather than one shared table with a species tweak bolted on.
Should I feed exactly what this says?
Treat it as a starting estimate, not an instruction. A vet's guidance, and the specific food's own feeding chart on the bag, should always take priority over a generic calculator — especially for puppies and kittens, pregnant or nursing animals, and any medical condition, none of which a formula like this one knows anything about.