Pet Food Portion Calculator

How much should you really feed your dog or cat?

Most pet food bags print a daily-portion table on the back. Those tables are useful starting points, but they are written by food manufacturers who lean toward larger portions — and they don't know your specific pet. The vet-recommended approach is to start from your pet's actual energy needs, calculated from weight and life stage, then adjust based on body condition over time.

The RER × MER formula in plain English

Vets calculate calorie needs in two steps. First, RER (Resting Energy Requirement) — the calories your pet would burn lying on the couch all day — using the formula 70 × weight_kg^0.75. Then we apply a MER multiplier (Maintenance Energy Requirement) for species, age, and activity. A growing puppy needs roughly 2.5× their RER, while a low-activity senior needs about 1.2×. This is the same formula used in veterinary nutrition textbooks — we just do the math for you.

Converting calories to cups or grams

Once you know daily calories, dividing by your food's calorie density gives you the portion. Typical averages: dog dry kibble 350-450 kcal/cup (we use 400), dog wet food 150-200 kcal/can, cat dry kibble 300-350 kcal/cup, and cat wet food 120-180 kcal/can. If your food has very different calorie density (premium kibble can run 500+ kcal/cup; weight-management formulas can run 250-300), use the kcal-per-cup on the back of the bag instead of our default midpoints.

Why activity only matters for adults

Puppies and kittens need extra calories for growth no matter how much they sleep, and senior pets have slower metabolisms regardless of how much they move around. Activity multipliers really only change adult calorie needs — that's why our calculator only uses your activity selection when you've chosen the Adult age stage.

How often to feed

Puppies and kittens do best with 3-4 small meals per day to support steady growth and stable blood sugar. Adult dogs and cats typically eat 2 meals per day — morning and evening works for most households. Senior pets often benefit from 2-3 smaller meals to ease digestion. Free-feeding (an always-full bowl) is generally a bad idea for cats and adult dogs: it makes overweight pets harder to spot until they're already obese.

A note on accuracy

These numbers are starting estimates. The biggest variables we can't see are your specific food's actual calorie density, your pet's body condition score (rib visibility, waist when viewed from above), and any health factors like spaying/neutering, weight goals, or chronic conditions. Always cross-check against your food's package and your vet's recommendation, especially for puppies, seniors, and pets with medical needs.