Portion guidance on a food label is written for an average cat, and most cats are not average. This calculator uses the same two-step energy equation veterinary teams use: work out the resting requirement from body weight, then apply the multiplier that matches the cat’s neuter status and life stage.
This is a starting point for a healthy cat, not a prescription. Cats vary by roughly 20–25% around a calculated requirement. Weigh the cat every two weeks and adjust: the trend on the scale is the real answer, not the equation. Any cat that needs to lose weight, or that has kidney, thyroid, diabetic or heart disease, needs a plan set by a veterinarian.
How this tool was built: methodology and sources
Two steps, both standard veterinary practice.
Step 1 — resting energy requirement. RER is the energy a cat uses at rest. It scales to body weight to the power of three quarters, not to body weight directly, which is why a cat twice as heavy does not need twice the food:
RER = 70 × (body weight in kg)0.75
Step 2 — daily requirement. RER is multiplied by a factor for the cat’s status:
| Status | Multiplier |
|---|---|
| Neutered adult | 1.2 × RER |
| Intact adult | 1.4 × RER |
| Adult prone to weight gain | 1.0 × RER |
| Healthy kitten | 2.5 × RER |
Why there is no weight-loss setting. Restricting a cat’s intake is genuinely dangerous without supervision: cats that stop eating can develop hepatic lipidosis within days. A deliberate weight-loss plan is calculated against a target weight and monitored by a veterinarian, so this tool does not offer one.
- Nutritional Requirements and Related Diseases of Small Animals. MSD/Merck Veterinary Manual — resting energy requirement equation and the feline maintenance multipliers used above. Reference page
- National Research Council. Nutrient Requirements of Dogs and Cats. Washington DC: National Academies Press, 2006 — the source of the allometric energy equation adopted in clinical practice.
- Quimby J, et al. 2021 AAHA/AAFP Feline Life Stage Guidelines. Journal of Feline Medicine and Surgery 2021;23(3):211–233 — for life-stage feeding and body condition monitoring. doi:10.1177/1098612X21993657