Dog & Cat Food Portion Calculator
PawPortions works out how much your dog or cat should eat each day from their weight, body shape, age and activity, then helps you stick to it with a daily treat allowance and a weight log. It uses the standard veterinary energy formulas, runs entirely on your device, and needs no account.
How it works
- Tell us about your pet: name, dog or cat, current weight, body shape, age, and how active they are.
- Add their food: scan the label with your phone camera (read on-device, never uploaded) or type the kcal/kg. If the label has no calorie figure, it's estimated from the protein, fat, fibre, ash and moisture. No bag to hand? Skip it and you'll get a calorie budget instead of grams.
- PawPortions sets a target weight from the body shape and calculates a daily portion in grams or cups, with a treat allowance.
- Log treats on the Today screen as you give them, and the remaining allowance updates instantly.
- Log weight over time to check the portion is working.
The calculation, step by step
PawPortions uses the standard small-animal energy model. First it estimates your pet's ideal weight from their current weight and body condition score (BCS) on the 1 to 9 scale. A score of 4 or 5 is treated as ideal, and each point above 5 is taken to mean roughly 10% over ideal, so ideal weight = current weight / (1 + 0.1 x (BCS - 5)). Next it calculates the resting energy requirement, RER = 70 x (ideal weight in kg)^0.75. Finally it multiplies RER by a factor for life stage, neutering, activity and goal to get the daily energy requirement.
For adult dogs the factor runs from 1.4 (low activity, neutered) to 3.0 (very active, not neutered), with 1.6 for a typical neutered dog and 1.8 for a typical intact one. For adult cats it runs from 1.0 to 1.6, with 1.2 for a typical neutered cat. Pets under 12 months use a growth factor of 2.0. For weight loss the factor is 1.0 x RER for dogs and 0.8 x RER for cats, and for weight gain it is 1.5 for dogs and 1.3 for cats. A cat's intake is never allowed to fall below 0.8 x RER, because rapid weight loss in cats can cause a life-threatening liver condition called hepatic lipidosis.
Treats are capped at 10% of the daily energy, and the remaining 90% is the food allowance. Grams per day is the food energy divided by the energy density printed on the bag, in kcal per kg. Cups are only shown if you enter a grams-per-cup figure, because a cup count based on an assumed density can be badly wrong.
Two worked examples
A neutered adult dog of 20 kg with a body score of 5 and typical activity: RER = 70 x 20^0.75 = 662 kcal, and the daily requirement is 662 x 1.6 = 1,059 kcal. Treats take up to 106 kcal, leaving 953 kcal for meals. On a food with 3,600 kcal per kg that is 265 g a day, or about 132 g for each of two meals.
A dog of 25 kg with a body score of 7 is about 20% over ideal, so the target weight is 25 / 1.2 = 20.8 kg. On the weight-loss plan the daily requirement is 1.0 x RER of that target weight, which is 683 kcal, leaving about 614 kcal for meals after the treat allowance, or about 171 g a day of the same food. A commonly recommended safe loss rate is 1 to 2% of body weight a week for dogs (0.5 to 1% for cats), which is why the weight log checks your trend against those limits.
When the tool will not give you a number
A general calculator is the wrong tool for puppies and kittens under four months, pregnant or nursing animals, animals with a diagnosed medical condition, and animals with a severe body condition score (8 or 9). In those cases PawPortions does not produce a figure and points you to your vet instead. It will still let you log weight.
Reading the label and checking the result
You can scan the food bag with your camera. The text is read on your device, using in-browser text recognition, and the image is never uploaded. If the label gives no calorie figure, PawPortions estimates one from the guaranteed analysis (protein, fat, fibre, ash and moisture), which is less precise than a printed kcal per kg figure, so use the printed value when it is available.
Every formula here describes an average animal, and individual pets can differ from the estimate by 20% or more. Treat the portion as a starting point and use the weight log to adjust: if your pet is gaining or losing faster than you intended, change the portion in small steps and review again after a few weeks. This tool is not veterinary advice. Your vet can account for health, breed and lifestyle in ways a formula cannot.
Frequently asked questions
How does PawPortions calculate daily calories?
It calculates a resting energy requirement (RER = 70 × kg^0.75) from your pet's target weight, then multiplies by a factor for life stage, neutering and activity (MER). The result is split into meals and a treat allowance of no more than about 10% of daily calories.
Does it work for cats as well as dogs?
Yes. Choose dog or cat when you add a pet; the body-shape guide and energy factors are species-specific.
When won't it give me a number?
For pets under four months, pregnant or nursing pets, pets with a diagnosed medical condition, or a severe body condition score, a general calculator is the wrong tool. PawPortions points you to your vet instead and still lets you log weight.
What counts as a treat?
Anything fed outside the main meals: commercial treats, table scraps, chews, training rewards and toppers. Small extras add up, so logging them keeps the budget accurate.
Is my pet's data stored on a server?
No. All pet profiles, food details and logs are stored locally on your device. Nothing is uploaded, and the tool works offline once loaded.
Can I track more than one pet?
Yes. Add as many dogs and cats as you like; each has its own portion, treat log and weight history. Switch with one tap at the top of the Today screen, see everyone's portion together on the Feeding time card, and give a new pet the same food as another in one tap.
Sources and further reading
Formulas checked against the sources below. Last reviewed . General information only, not professional advice.