Food & Cooking⏱ 4 min read
How to Calculate How Much to Feed Your Cat
Overfeeding is the leading cause of feline obesity. Here is how to calculate your cat's daily calorie needs by weight, life stage, and activity level — and how to convert that to food portions.
Most cat owners rely on the "suggested feeding" guidelines on pet food packaging — which are deliberately broad and often lead to overfeeding. Calculating your cat's individual needs produces a more precise, healthier portion size.
Resting Energy Requirement (RER)
RER is the base metabolic energy need for cats at rest.
RER (kcal/day) = 70 x (body weight in kg)^0.75
Example: 4.5kg neutered adult cat:
RER = 70 x (4.5)^0.75
4.5^0.75: ln(4.5) = 1.504, x 0.75 = 1.128, e^1.128 = 3.089
RER = 70 x 3.089 = 216 kcal/day
Daily Energy Requirement (DER) by Life Stage
DER = RER x Life Stage Multiplier
Life stage multipliers:
Kitten (4 months to 1 year): RER x 2.0-2.5
Intact adult cat: RER x 1.4
Neutered adult (lean): RER x 1.2
Neutered adult (prone to weight gain): RER x 1.0
Pregnant cat (mid-late): RER x 1.6-2.0
Nursing cat: RER x 2.0-6.0 (depending on litter size)
Senior cat (7+ years, lean): RER x 1.1
Obese cat (weight loss goal): RER x 0.8
Example: 4.5kg neutered adult (lean): 216 x 1.2 = 259 kcal/day
Converting Calories to Food Portions
Find the kcal/100g (or per can/pouch) on the pet food packaging.
Usually listed as "metabolisable energy" or "kcal/100g"
Typical calorie densities:
Wet food (pâté/chunks in gravy): 70-100 kcal/100g
Dry kibble: 350-400 kcal/100g
Raw food (complete): 100-150 kcal/100g
For 259 kcal/day target, wet food at 85 kcal/100g:
Weight of food = 259 / 85 x 100 = 304.7g per day
Two meals: 152g per meal (approx two standard 150g pouches)
For dry kibble at 370 kcal/100g:
Weight = 259 / 370 x 100 = 70g per day -- weigh this; don't guess!
Weight Loss Calculation for Overweight Cats
First: establish current weight and ideal weight.
Use body condition score (BCS) 1-9 scale; ideal is 4-5.
For a BCS 7 (overweight) 6kg cat whose ideal weight is 4.5kg:
Use IDEAL weight for RER calculation (not current weight)
RER of ideal weight (4.5kg): 216 kcal/day
Weight loss DER multiplier: 0.8
Daily calories for weight loss: 216 x 0.8 = 173 kcal/day
Expected weight loss rate at this calorie level:
Approximately 0.5-1% of body weight per week
For 6kg cat: 30-60g/week -- safe rate for feline weight loss
Never fast a cat or reduce to below 0.8 x RER of ideal weight.
Hepatic lipidosis (fatty liver disease) can develop in under-fed cats within days.