Cat Food Calculator: Daily Calories and Cups per Day

To work out how much to feed a cat you need two numbers: the cat’s daily calorie needs, and the calories in its food. The calculator estimates the first with the standard veterinary formula and the life-stage factors in the Merck Veterinary Manual, then divides by the calorie content you read from the label.

Step 1: resting energy requirement (RER)

RER (kcal/day) = 70 × (body weight in kg)^0.75

This is the energy a cat uses at rest. To convert pounds to kilograms, divide by 2.2046.

Step 2: life-stage factor

The Merck Veterinary Manual lists these multipliers for cats:

Cat	Factor (× RER)
Adult, spayed/neutered	1.2
Adult, intact	1.4
Obesity-prone or inactive	1.0
Kitten	2.5 (or free choice)

The calculator starts at 1.2, the factor for a spayed or neutered adult; change it if that doesn’t describe your cat.

Step 3: subtract treats, then convert

WSAVA (the World Small Animal Veterinary Association) advises that treats should make up less than 10% of a cat’s daily calories. The calculator takes the treat share out first and divides the rest by the food’s kcal per cup.

Daily calories by weight

Weight	RER	Neutered adult (1.2)	Intact adult (1.4)	Inactive (1.0)	Kitten (2.5)
6 lb	148	178	208	148	371
8 lb	184	221	258	184	460
10 lb	218	261	305	218	544
12 lb	249	299	349	249	624
14 lb	280	336	392	280	700
16 lb	310	371	433	310	774

kcal per day, rounded. For an overweight cat, the weight to use is a question for your vet.

Worked examples

Example 1: a 10 lb neutered adult cat, dry food with 400 kcal per cup, 10% treats. 10 lb = 4.54 kg. 4.54^0.75 = 3.11. RER = 70 × 3.11 = 218 kcal. MER = 218 × 1.2 = 261 kcal per day. Treats: 26 kcal. Food: 261 − 26 = 235 kcal ÷ 400 = 0.59 cups per day (a little over half a cup). Normal variation (±50%): 131–392 kcal.

Example 2: the same cat on wet food. Daily target 261 kcal, minus 26 for treats = 235 kcal. With a can labeled 80 kcal, that’s 235 ÷ 80 ≈ 2.9 cans per day. (Check your own label; calorie content varies a lot between foods.)

Example 3: a 2 kg (4.4 lb) kitten. RER = 70 × 2^0.75 = 118 kcal. × 2.5 = 294 kcal per day.

Limitations

• Wide individual variation. AAHA’s nutrition guidelines note up to 50% difference either way between calculated and actual needs in cats. Weigh your cat regularly and adjust.
• Weight loss, pregnancy and nursing are left out on purpose: they need a veterinarian’s plan.
• Medical conditions such as kidney disease, diabetes or hyperthyroidism change what and how much a cat should eat.
• Scoops vary. Weighing dry food in grams (using the kcal/kg on the label) is more accurate than cups.