# How many cat calories per day?

Estimates a cat’s daily calories from its weight and life stage: the resting energy requirement 70 × kg^0.75 times the Merck Veterinary Manual factor.

- Page: https://www.acalculator.org/biology/cat-calorie-calculator
- JSON spec: https://www.acalculator.org/biology/cat-calorie-calculator.json
- Version: d0690babab5c

## Default answer

Example with the default inputs (Cat’s weight 10 lb, Life stage Neutered adult (× 1.2)): A 10 lb cat needs about 261 calories a day at 1.2 × RER.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| w | Cat’s weight | Your cat’s body weight now (use the ideal weight your vet gives for a weight-loss plan). |
| stage | Life stage | The life stage or activity, which sets the factor on the resting energy. |
| food | Food calories per cup or can | From the food label, in kcal per cup or per can. Leave empty to skip. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| daily | Calories per day | RER × the life-stage factor. |
| rer | Resting energy (RER) | 70 × body weight in kg raised to the power 0.75. |
| factor | Life-stage factor | The Merck Veterinary Manual multiplier for this life stage. |
| portions | Cups or cans per day | Calories per day ÷ the food’s calories per cup or can. |

## Method

RER = 70 × (body weight in kg)^0.75 kcal a day; calories per day = RER × the life-stage factor (neutered adult 1.2, intact adult 1.4, inactive or obesity prone 1.0, kitten 2.5); cups or cans = calories ÷ the food’s calories per cup or can.

## Assumptions

- The factors are the Merck Veterinary Manual’s for healthy cats. Each cat differs, so the result is a starting point: weigh your cat every few weeks and adjust.
- For weight loss, ask your vet for a target weight and plan; this page does not give a weight-loss factor.
- Pregnant, nursing and sick cats need a vet’s plan. This page is for information only and is not veterinary advice.

## Worked examples

1. w = 5, stage = neutered gives rer = 234.059107, daily = 280.870928. Source: Merck Veterinary Manual, Nutritional Requirements of Small Animals (S. L. Sanderson, reviewed Nov 2023): RER = 70 × BW(kg)^0.75; kittens 2.5 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals.
2. w = 4.535924, stage = intact, food = 400 gives rer = 217.569165, daily = 304.596831, portions = 0.761492. Source: Merck Veterinary Manual, Nutritional Requirements of Small Animals (S. L. Sanderson, reviewed Nov 2023): RER = 70 × BW(kg)^0.75; kittens 2.5 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals.
3. w = 1.5, stage = kitten gives rer = 94.87821, daily = 237.195526, factor = 2.5. Source: Merck Veterinary Manual, Nutritional Requirements of Small Animals (S. L. Sanderson, reviewed Nov 2023): RER = 70 × BW(kg)^0.75; kittens 2.5 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals.
4. w = 1, stage = prone gives rer = 70, daily = 70. Source: Merck Veterinary Manual, Nutritional Requirements of Small Animals (S. L. Sanderson, reviewed Nov 2023): RER = 70 × BW(kg)^0.75; kittens 2.5 × RER, https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals.

## FAQ

### How many calories does a cat need a day?

A 10 lb (4.54 kg) neutered adult cat needs about 70 × 4.54^0.75 × 1.2 = 261 kcal a day. An intact cat of the same weight needs about 305 kcal, and a 5 kg neutered cat about 281 kcal.

### What is RER?

The resting energy requirement: the calories a cat burns at rest in a comfortable room. RER = 70 × body weight in kg raised to the power 0.75.

### What factor should I use for my cat?

The Merck Veterinary Manual gives 1.2 × RER for a neutered adult, 1.4 × RER for an intact adult, 1.0 × RER for an obesity-prone cat, and 2.5 × RER for kittens (which can also be fed free choice).

### How do I turn calories into food?

Find the kcal per cup or per can on the food label and type it. A 10 lb intact cat at 305 kcal a day, on dry food with 400 kcal per cup, needs 0.76 cup a day. Treats count too.

### How do I feed a cat that needs to lose weight?

Ask your vet for a target weight and a plan. Weight loss in cats should be slow, and a cat that stops eating can become ill. This page does not give a weight-loss factor.

### Why is the weight raised to the power 0.75?

Energy use grows more slowly than body weight: a cat twice as heavy needs about 2^0.75 = 1.68 times the calories, not twice as many.

## Sources

- Merck Veterinary Manual, Nutritional Requirements of Small Animals, by Sherry Lynn Sanderson (full review Nov 2023): RER = 70 × BW(kg)^0.75; daily maintenance energy for cats: intact 1.4, neutered 1.2, obesity prone 1 × RER; kittens 2.5 × RER. https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals (retrieved 2026-10-02)
- National Research Council, Nutrient Requirements of Dogs and Cats (2006), Chapter 3, Energy (the energy requirements these factors build on). https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats (retrieved 2026-10-02)
- NIST Special Publication 811, Appendix B (1 lb = 0.45359237 kg exactly). https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-02)