This calculator uses RER (Resting Energy Requirement) — the energy a pet needs at complete rest — scaled up by a life-stage/activity factor to estimate MER (Maintenance Energy Requirement), the actual daily target.

The 0.75 exponent reflects how metabolism scales with body size: a 40 kg dog doesn’t need twice the calories of a 20 kg dog, only around 1.6×. This exponential formula (rather than a flat per-kg estimate) is the version endorsed by veterinary nutrition bodies for animals of any size.

The factor then adjusts for how that baseline is spent day to day:

• Growing puppies/kittens need more per kg than adults
• Spayed/neutered adults typically need less than intact adults
• Inactive or weight-loss cases use a lower factor; working or highly active animals use a higher one

On accuracy: this formula is a population-level starting point, not a diagnosis. Published veterinary sources note that individual animals can vary by up to ±50% from the calculated value depending on metabolism, breed, climate, and health status. Use the result as a starting portion, then adjust up or down based on your pet’s actual body condition over a few weeks — and check with a vet for puppies/kittens, pregnant or nursing animals, or any pet with a medical condition.