How many calories does a cat need per day?

An average 4kg neutered indoor cat needs approximately 200-250 kcal per day. However, this varies significantly based on weight, activity level, body condition, and life stage. Kittens need proportionally more, and senior cats typically need less.

Should indoor cats eat less than outdoor cats?

Yes. Indoor cats are significantly less active and need 20-30% fewer calories than outdoor cats of the same weight. This is the single biggest factor in indoor cat obesity, which affects over 60% of cats in developed countries.

How do I know if my cat is overweight?

Use the feline Body Condition Score (BCS). At ideal weight (BCS 5/9): you can feel ribs with light pressure, there's a visible waist from above, and a slight tummy tuck from the side. If you can't feel ribs, or there's no visible waist, your cat is likely overweight.

What is the RER formula for cats?

RER (Resting Energy Requirement) = 70 x (body weight in kg)^0.75. This is the same allometric scaling formula used for dogs, validated by the National Research Council for feline nutrition. MER (Maintenance Energy Requirement) then adjusts RER for life stage and activity.

NRC feline formula

Cat Calorie Calculator

How many calories does your cat actually need? Enter their weight, life stage, and activity level. We'll give you a precise daily target using the NRC feline RER formula — the same one veterinary nutritionists use.

Your cat's weight ?

Life stage

Activity level

Body condition (1-9 scale) ?

Daily Calorie Target

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RER (kcal)

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multiplier

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wet food (g)

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How We Calculate Your Cat's Calories

We use the NRC (National Research Council) feline RER formula — the same allometric scaling equation used for dogs, validated specifically for cats:

RER = 70 × (body weight in kg)^0.75

This gives the resting energy requirement — the calories your cat would burn lying still. We then multiply by a life-stage factor to get the Maintenance Energy Requirement (MER), and adjust for activity level and body condition.

Life Stage Multipliers

Life Stage	Multiplier
Kitten (under 12 months)	2.5 × RER
Adult — neutered/spayed	1.2 × RER
Adult — intact	1.4 × RER
Senior (over 11 years)	1.1 × RER
Pregnant	1.6 × RER
Lactating	2.0-6.0 × RER

Why Indoor Cats Need Less

Indoor cats are dramatically less active than outdoor cats. Studies show indoor cats may sleep 16-20 hours per day and cover only a fraction of the distance outdoor cats travel. This reduced energy expenditure means indoor cats need 20-30% fewer calories — yet most owners feed the same amount, which is a primary driver of the feline obesity epidemic.

Over 60% of cats in developed countries are classified as overweight or obese, with indoor cats disproportionately affected.

Frequently Asked Questions

An average 4kg neutered indoor cat needs approximately 200-250 kcal per day. But this varies based on weight, activity, body condition, and life stage. Kittens need proportionally more, senior cats typically less. Our calculator accounts for all these factors.

Yes, significantly. Indoor cats need 20-30% fewer calories. This is the single biggest factor in indoor cat obesity. Our calculator applies an activity adjustment for indoor-only cats.

Use the feline Body Condition Score (BCS). Ideal is 5/9: ribs felt with light pressure, visible waist from above, slight tummy tuck. If you can't feel ribs, or there's a hanging belly, your cat is likely overweight. Over 60% of cats in developed countries are classified as overweight.

RER = 70 × (body weight in kg)^0.75. This allometric scaling formula accounts for the fact that metabolic rate doesn't scale linearly with body weight. It's validated by the NRC for both cats and dogs and used by veterinary nutritionists worldwide.

Sources & References

1
NRC Nutrient Requirements of Dogs and Cats (2006)
National Academies Press • Feline energy requirements and RER formula
2
WSAVA Global Nutrition Guidelines — Feline Section
World Small Animal Veterinary Association • BCS system and feeding protocols
3
Association for Pet Obesity Prevention — 2023 Survey
APOP • Feline obesity prevalence data and indoor cat activity research