Food & Cooking⏱ 4 min read
How to Calculate the Right Amount of Food for Your Cat
Feeding guides on cat food packaging are widely over-generous. Here is how to calculate the correct daily amount for your cat's weight, age, neutered status, and whether it goes outdoors.
Feline obesity affects an estimated 40-50% of UK cats, and excessive feeding is the primary driver. Unlike dogs, cats are obligate carnivores with specific caloric needs — and those needs are frequently overestimated by manufacturers.
Resting Energy Requirement for Cats
RER (kcal/day) = 70 x (Body weight in kg)^0.75
Examples:
3kg cat: 70 x 3^0.75 = 70 x 2.28 = 160 kcal/day (RER)
4.5kg cat: 70 x 4.5^0.75 = 70 x 3.08 = 216 kcal/day
6kg cat: 70 x 6^0.75 = 70 x 3.83 = 268 kcal/day
Daily Energy Requirement Multipliers
Multiply RER by the appropriate life stage factor:
Neutered adult, indoor only: x 1.2
Neutered adult, indoor/outdoor: x 1.4
Intact adult, indoor: x 1.4
Active outdoor cat: x 1.6
Kitten (under 6 months): x 2.5
Kitten (6-12 months): x 2.0
Overweight cat (weight loss): x 0.8-1.0 (feed to IDEAL weight)
Senior cat (7+): x 1.1-1.3 (metabolism slows but protein needs rise)
Example: 4.5kg neutered indoor cat
RER: 216 kcal
DER: 216 x 1.2 = 259 kcal/day
Typical bag recommendation: ~320 kcal (overfeeding by 24%)
Converting to Food Quantities
Check kcal per 100g on your cat food:
Dry food: 330-420 kcal per 100g (check label)
Wet food (pouch): 70-100 kcal per 100g
Wet food (tin): 60-90 kcal per 100g
Example: 259 kcal daily need
Dry food at 380 kcal/100g: 259/3.8 = 68g per day
Wet food at 85 kcal/100g: 259/0.85 = 305g per day (approx 2 standard pouches)
Mixing wet and dry (common approach):
1 pouch wet (85g at 85 kcal/100g = 72 kcal) + dry
Remaining: 259 - 72 = 187 kcal from dry
Dry needed: 187/3.8 = 49g dry food
Body Condition Scoring
Numbers are guides — visual assessment is essential. A healthy-weight cat should have:
- Ribs that can be felt easily but not seen
- A visible waist when viewed from above
- A slight abdominal tuck when viewed from the side
If ribs are difficult to feel under fat, reduce daily intake by 10-15% and recheck in 4 weeks. Don't dramatically cut calories — in cats, rapid weight loss can cause hepatic lipidosis (fatty liver disease).