The calculator separates three questions: how many calories the pet may need, how many grams of this exact food provide those calories, and whether a cup estimate is useful for people using US-style household measures.
The calorie estimate uses a standard veterinary energy approach based on body weight in kilograms. It is a population-level starting point and is not a body-condition assessment.
The estimate is adjusted for dog or cat and broad life-stage goals. Adult, growth, neuter status, obesity-prone, and weight-loss selections use different starting values. Weight-loss values should be treated as supervised estimates, especially for cats.
Grams per day come from daily calories divided by the food's calorie density. If the label says kcal/100g, the calculator converts it to kcal/kg internally. This is why 400 g of wet food and 400 g of dry food can produce very different calories: the calorie-density input is different.
For weight-loss style selections, the chart shows a guideline monitoring band rather than an exact prediction. It uses commonly cited veterinary weekly weight-loss rates: about 1-2% body weight per week for dogs and about 0.5-1% per week for cats. Maintenance and growth selections show monitoring only because this calculator does not know body condition score, target weight, activity, illness, or treats.