Quick answer: A cat food calculator works out your cat's daily food portion from its body weight, life stage and activity level. It applies the veterinary formula RER = 70 x (weight in kg)^0.75, multiplies by an activity factor (1.2 for a typical neutered indoor cat, 2.5 for a kitten), then divides the daily calories by your food's kcal per cup.
Last reviewed: September 2026
Key facts
- RER = 70 × (weight in kg)0.75 — the standard resting-energy formula used in veterinary nutrition.
- Daily calories (MER) = RER × activity factor: 1.2 neutered indoor adult, 1.4 active, 2.5 kittens, 1.0 weight loss.
- Cats are obligate carnivores — they need animal protein and taurine, not plant-heavy diets.
- Wet food holds far fewer calories per gram than dry food because of its high moisture content.
Use this cat food calculator daily feeding guide to estimate how many calories your cat needs each day from body weight and activity level, using the veterinary resting-energy formula RER = 70 × weight0.75. It converts that calorie target into cups per day using your food's kcal per cup, giving a precise daily feeding amount — and because cats are obligate carnivores, it also explains what those calories should be made of.
Enter your cat's weight, life stage and food energy to get the daily calorie target and portion size. No sign-up, works on mobile and desktop.
How to use
- Enter your cat's weight (use ideal weight if overweight) and pick kg or lb.
- Choose the life stage / activity level that best matches your cat.
- Enter your food's kcal per cup from the package label.
- Read the daily cups and the per-meal portion.
How cat food portions are calculated
| Term | Meaning |
|---|---|
| RER | Resting energy requirement: calories a cat burns at rest in a day. |
| Factor | Activity/life-stage multiplier (1.0–2.5). |
| MER | Maintenance energy requirement: total daily calories needed. |
| kcal/cup | Your food's energy density, printed on the label. |
Cats need proportionally fewer activity calories than dogs, but kittens are the exception: growth can push needs to 2.5 × RER.
Background: why cat nutrition is a special science
The calorie math for cats borrows the same RER base as dogs, but feline metabolism follows stricter rules. Cats are obligate carnivores: unlike dogs, they cannot synthesize enough taurine, arachidonic acid or preformed vitamin A (retinol) from plant precursors, so these nutrients must come from animal tissue. The taurine requirement was only nailed down in the 1970s, after researchers linked taurine-deficient commercial diets to feline central retinal degeneration and dilated cardiomyopathy — a landmark episode that reshaped pet food formulation worldwide.
The U.S. National Research Council's Nutrient Requirements of Dogs and Cats (2006) sets the energy and nutrient baselines behind this calculator's factors, while AAFCO's cat food nutrient profiles translate them into the minimums every complete commercial cat food must meet. The lower activity factors for cats (1.2–1.4 for adults versus 1.6–1.8 for dogs) reflect a real physiological difference: cats are ambush predators built for short bursts, not endurance, so a neutered indoor cat's maintenance needs sit much closer to resting.
Cat food calculator daily feeding guide by life stage
The table below combines the calculator's MER factors with practical feeding schedules for each stage of a cat's life:
| Life stage | MER factor × RER | Meals per day | Notes |
|---|---|---|---|
| Kitten (growing) | 2.5 | 3–4 | Feed a growth/kitten formula; needs peak before 6 months |
| Neutered indoor adult (typical) | 1.2 | 2 | The most common profile; obesity risk is highest here |
| Active / outdoor adult | 1.4 | 2 | Hunting and roaming raise expenditure modestly |
| Intact adult | 1.4 | 2 | Similar to active outdoor |
| Senior / low activity | 1.0–1.1 | 2 | Watch muscle loss, not just weight; protein stays important |
| Pregnant / lactating queen | 2.0–4.0 | 3+ | Needs can quadruple at peak lactation; feed kitten formula |
| Weight loss plan | 1.0 × ideal weight | 2–3 | Always use target weight; cats must lose weight slowly to avoid hepatic lipidosis |
Use this as a fast starting point; adjust to your cat's body condition over two to four weeks.
| Cat weight | Daily calories | Dry food (400 kcal/cup) | Wet food (85 kcal/3 oz can) |
|---|---|---|---|
| 5 lb (2.3 kg) | ~155 kcal | ~0.4 cup | ~1.8 cans |
| 8 lb (3.6 kg) | ~220 kcal | ~0.55 cup | ~2.6 cans |
| 10 lb (4.5 kg) | ~260 kcal | ~0.65 cup | ~3.1 cans |
| 12 lb (5.4 kg) | ~300 kcal | ~0.75 cup | ~3.5 cans |
| 15 lb (6.8 kg) | ~355 kcal | ~0.9 cup | ~4.2 cans |
| Cat weight | Daily calories | Dry food (400 kcal/cup) | Wet food (85 kcal/3 oz can) |
|---|---|---|---|
| 5 lb (2.3 kg) | ~155 kcal | ~0.4 cup | ~1.8 cans |
| Cat | Factor × RER |
|---|---|
| Neutered indoor adult | 1.2 |
| Active / outdoor adult | 1.4 |
| Kitten (growing) | 2.5 |
| Senior / low activity | 1.0–1.1 |
| Weight loss | 1.0 |
Frequently asked questions
Is the dog formula the same as the cat formula?
The RER base formula is the same (70 × kg^0.75), but cats use lower activity factors: 1.2 for a neutered indoor adult versus 1.6 for a neutered adult dog. Kittens are the main exception, needing up to 2.5 × RER while growing.
How much wet food equals a cup of dry food?
Wet food is roughly 75–80% water, so it holds far fewer calories per gram. A 3 oz can typically provides 70–100 kcal versus 300–450 kcal per cup of dry food. Always compare foods by calories, not by volume: subtract the wet food's calories from the daily target and fill the rest with measured dry food.
How many times a day should I feed my cat?
Most adult cats do well on 2 measured meals per day. Kittens under 6 months need 3–4 meals a day to support growth. Avoid free-feeding dry food all day for indoor cats — it is a common cause of obesity.
Can I feed my cat dog food?
No. Cats are obligate carnivores and need nutrients dog food lacks — especially taurine, arachidonic acid and preformed vitamin A. Long-term dog-food feeding can cause serious deficiencies, including blindness and heart disease.
How much should I feed my cat per day?
An average adult cat needs roughly 200 to 300 calories a day, adjusted for weight, age, and activity. The veterinary formula is 70 x (weight in kg)^0.75 for resting energy needs, multiplied by a lifestyle factor. Weigh your cat regularly and adjust portions to hold a healthy weight.
How do I know if I am feeding my cat the right amount?
Check your cat's body condition every two to four weeks rather than watching the bowl. You should be able to feel the ribs under a light layer of fat, see a defined waist from above, and notice a slight tuck at the belly from the side. If the ribs are hidden or the waist is gone, trim the daily portion by about 10% and re-weigh in two weeks.
Sources
- AAFCO — Dog and cat food nutrient profiles and feeding guidance
- National Research Council (2006) — Nutrient Requirements of Dogs and Cats: energy and taurine requirements
- WSAVA — Global Nutrition Guidelines for companion animals
Key takeaways
- Daily calories = 70 × (kg)0.75 × activity factor (1.2 for typical indoor cats) — the basis of this cat food calculator daily feeding tool.
- Kittens need up to 2.5 × RER while growing — a 2 kg kitten can out-eat a 4 kg adult.
- Compare foods by calories per serving, not volume — wet and dry differ hugely.
- Two measured meals a day beats free-feeding for weight control.
- Calories must come with complete nutrition: animal protein, taurine, arachidonic acid and vitamin A.
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