Healthy adult cat
4.5 kg, 3 years, neutered, moderate activity.
260 kcalRER = 70 × 4.50.75 = 216.3. Then 216.3 × 1.2 = 259.6, rounded to 260.
At 400 kcal per cup, that is 5/8 cups a day, or about 3/8 cups at each of 2 meals.
Cat Calorie Calculator
Enter your cat’s details to estimate daily calories and food portions. Everything is calculated in your browser, and nothing is sent anywhere.
Cat Calorie Calculator result
readway.site/cat-calorie-calculator/
Daily calories for your cat
Fill in your cat’s details and press Calculate. Your daily calories, food portions, and the math behind them will appear here.
No cat on hand? Press Use example to see a sample.
How the calculator works
Cats burn energy even when they rest. The calculator first estimates that resting energy. It then adds the energy your cat needs for a normal day, based on age, activity, and whether your cat is spayed or neutered.
If your cat is overweight or too thin, the tool plans around an ideal weight instead. That keeps weight loss slow and weight gain steady.
If you enter food calories, the tool divides the daily total by the calories in each cup, kilogram, or can. That gives you the amount to feed.
The formula and factors
Resting Energy Requirement (RER) = 70 × (weight in kg)0.75
Daily target = RER × factor. The factor depends on your cat:
| Situation | Factor |
|---|---|
| Under 4 months | 3.0 × RER |
| 4 to under 6 months | 2.5 × RER |
| 6 to under 12 months | 2.0 × RER |
| Adult, spayed or neutered, moderate activity | 1.2 × RER |
| Adult, not neutered, moderate activity | 1.4 × RER |
| Low activity | adult factor × 0.85 |
| High activity | adult factor × 1.15 |
| Weight loss | 0.8 × RER at ideal weight |
| Weight gain | 1.2 × RER at ideal weight (never less than maintenance) |
If you do not enter an ideal weight, the tool estimates one. It assumes an overweight cat is about 15% above ideal, an obese cat about 35% above, and a thin cat about 20% below.
Rounding rules
- RER is rounded to one decimal place before it is multiplied.
- Daily calories are rounded to the nearest whole kcal.
- The practical range is 10% below and above the daily target.
- Cups are rounded to the nearest 1/8 cup. Amounts under 1/4 cup are shown in tablespoons.
- Grams are rounded to whole grams. Cans are rounded to the nearest 1/4 can.
- A cup means a standard US measuring cup (8 fluid ounces).
Typical daily calories by weight
Adult cats at a healthy weight with moderate activity:
| Weight | RER (kcal) | Neutered (kcal/day) | Not neutered (kcal/day) |
|---|---|---|---|
| 3 kg (6.6 lb) | 159.6 | 192 | 223 |
| 4 kg (8.8 lb) | 198.0 | 238 | 277 |
| 5 kg (11.0 lb) | 234.1 | 281 | 328 |
| 6 kg (13.2 lb) | 268.4 | 322 | 376 |
| 7 kg (15.4 lb) | 301.2 | 361 | 422 |
Worked examples
These numbers come from the same code the calculator uses.
Three-month-old kitten
1.2 kg, 3 months old.
241 kcalRER = 70 × 1.20.75 = 80.3. Under 4 months the factor is 3.0, so 80.3 × 3.0 = 240.9, rounded to 241.
Recheck every week or two as weight rises.
Overweight adult cat
6 kg now, ideal weight 5 kg, neutered, low activity.
187 kcalRER at 5 kg = 234.1. For weight loss use 0.8, so 234.1 × 0.8 = 187.3, rounded to 187.
Aim to lose about 30 to 120 g per week.
Common mistakes
- Forgetting the treats.Treats count. Try keeping them to 10% of daily calories, and use the treat box above.
- Guessing the weight.Use a scale. A cat that looks 4 kg may weigh 5.
- Mixing up the food label.Check that you picked kcal per cup, per kg, or per can to match the number you typed.
- Counting only one food.Add up wet food, dry food, and toppings. They all carry calories.
- Cutting calories too fast.Fast loss can harm the liver. Go slowly and weigh every 2 weeks.
- Setting an ideal weight by eye.If you are unsure, leave it blank or ask your vet for a target.
Cat Calorie Calculator FAQ
How many calories does a cat need per day?
It depends on weight, age, activity, and whether the cat is spayed or neutered. A healthy 4.5 kg (about 10 lb) adult cat that is neutered and moderately active needs about 260 kcal a day. Use the calculator for your own cat.
What is RER?
RER stands for Resting Energy Requirement. It is the energy a cat uses to stay alive while resting in a warm place. The common formula is 70 × weight in kg to the power of 0.75.
What is MER, and why multiply RER?
MER is Maintenance Energy Requirement, the calories a cat needs for a normal day. Cats move, play, digest food, and grow, so they use more than RER. Vets multiply RER by a factor to cover this. For a spayed or neutered adult the base factor is 1.2. For a cat that is not neutered it is 1.4.
Where do I find the calories in my cat’s food?
Look at the bag or can. Most US labels show kcal per kg and also kcal per cup or per can. Use the number marked ME or kcal. If your food does not show it, check the brand’s website or ask the maker.
Do I count wet food and dry food together?
Yes. Add up the calories from everything your cat eats. If you feed both, work out how many calories each food should supply, then divide by that food’s calories per cup, kg, or can. Wet food has a lot of water, so it has fewer calories per gram than dry food.
How fast should my cat lose weight?
A common goal is about 0.5% to 2% of body weight per week. For a 6 kg cat, that is about 30 to 120 grams a week. Faster loss can harm the liver, so weigh your cat every 2 weeks and talk to your vet.
How accurate is the result?
It is a good starting point, not an exact number. Real cats can differ from the average by 10% or more. The tool shows a practical range of 10% above and below. Weigh your cat every 2 weeks and adjust the amount if weight moves in the wrong direction.
When should I see a vet instead?
See a vet before changing food if your cat is pregnant or nursing, is sick or on medicine, is too thin, is losing or gaining weight fast, or is a kitten with slow growth. Cats with long-term health problems often need a special diet.
This tool gives estimates for general information. It is not veterinary advice. Read the Disclaimer.