Cat calorie calculator
Get a daily calorie target for your cat: a 3-year-old, 4.5 kg cat with a sedentary routine needs about 260 kcal a day, from a resting need of 216.28 times 1.2. Kittens and seniors use their own factors. Free in your browser.
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Worked example
- Weight (kg)
- 4.5
- Age (years)
- 3
- Activity
- Sedentary
- Life stage
- adult
- Rer kcal
- 216.28
- Age factor
- 1
- Activity factor
- 1.2
The cat calorie calculator estimates a house cat's daily energy requirement in kilocalories from body weight, age, and activity level. Veterinary nutrition starts from the resting energy requirement, the exponential rule seventy times body weight in kilograms to the power of three-quarters, then scales that rest figure by a life-stage factor from age and an activity factor from how much the cat actually moves. Indoor adults, growing kittens, and quieter seniors therefore land on different daily targets even at the same weight.
What the resting energy formula is and how age and activity scale it
Veterinary feeding plans for domestic cats start from resting energy requirement, not from a human calorie table and not from the kilocalories printed on a bag of kibble. The exponential resting energy formula used in small-animal nutrition is RER equals seventy times body weight in kilograms raised to the power of three-quarters.
That three-quarters exponent is the metabolic scaling of Kleiber's law applied to a mammal whose surface-to-mass ratio is not linear in kilograms, so a four-and-a-half kilogram indoor adult does not need twice the energy of a two-and-a-quarter kilogram cat. Once RER is known, a life-stage factor from age and an activity factor from how much the animal actually moves convert rest into a maintenance energy requirement, MER. Kittens from four months to one year use 2.0.
Adults from one year up to seven years use 1.0. Seniors from seven years use 0.9 because many indoor older cats lower their daily expenditure. A four-and-a-half kilogram three-year-old sedentary cat therefore lands near two hundred and sixty kilocalories a day, which is the order of magnitude a clinic feeding chart would quote before you still confirm body-condition score with a veterinarian.
The linear shortcut thirty times kilograms plus seventy is not used here: it is a rough stand-in for medium dogs and mid-size cats, and it drifts on kittens and on very small or very large bodies where the three-quarters power law is the published veterinary default.
Where a cat calorie calculator earns its keep
Homes that have just adopted an indoor adult use a cat calorie calculator so the first week of feeding is not a guess copied from the neighbour's Maine Coon. Rescue intake desks and clinic front desks batch weight, age, and a coarse activity flag from the card and need a deterministic oracle that rejects a zero-kilogram paste instead of silently publishing a zero-calorie ration. Kitten foster programmes need the growth band (age under one year) to raise the multiple without someone memorising a wall chart for four months versus six.
Failed validation does not consume balance. Related searches for a human TDEE table, a cat-age-in-human-years conversion, or a kibble bag's kcal per cup are different intents: stay on this page when the question is only the cat's daily calorie requirement implied by weight, age, and activity. This estimate is educational and does not replace a veterinarian, especially for obese, underweight, pregnant, lactating, or clinically ill cats whose coefficients sit outside the four activity labels.
What you can do with it
Indoor adult feeding plan
Enter the cat's weight in kilograms, adult age, and sedentary activity to get a daily kilocalorie target you can split across wet and dry meals.
Kitten growth rations
Foster and clinic intake cards for cats under one year use the kitten age factor so the daily target rises with growth instead of copying an adult indoor chart.
FAQ
How is a cat's daily calorie need calculated?
Resting energy is 70 times body weight in kilograms to the power 0.75.
What happens if weight is zero or negative?
Weight must be a finite positive number of kilograms; a zero or negative mass is not a body that has a resting energy requirement, and the failure is not billed.
How many calories does a 4.5 kg indoor cat need?
A 3-year-old adult of 4.5 kg with a sedentary routine has a resting need of 216.28 kcal; multiplied by 1.2 for activity, that comes to about 260 kcal per day.
How does age change the calorie target?
Kittens under four months use a factor of 2.5 and kittens up to one year use 2.0, because growth adds to their needs. Adults from one to seven years use 1.0.
Which activity level should I choose?
Sedentary, 1.2, fits a typical neutered indoor cat; moderate, 1.4, a mixed indoor and outdoor day; active, 1.6, a working or outdoor cat; and very active, 1.8, a highly athletic animal.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/bio/catculator \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"weight_kg":4.5,"age_years":3,"activity":"sedentary"}'const res = await fetch("https://api.kit.forhosting.com/bio/catculator", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"weight_kg": 4.5,
"age_years": 3,
"activity": "sedentary"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/bio/catculator",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"weight_kg": 4.5,
"age_years": 3,
"activity": "sedentary"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/bio/catculator", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"weight_kg":4.5,"age_years":3,"activity":"sedentary"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"weight_kg":4.5,"age_years":3,"activity":"sedentary"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/bio/catculator", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"weight_kg": 4.5,
"age_years": 3,
"activity": "sedentary"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "bio.catculator",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_weight_kg | 40 |
max_age_years | 30 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Enter weight_kg, age_years, and one of sedentary, moderate, active, or very_active.
What the resting energy formula is and how age and activity scale it
Young kittens under four months, meaning age_years below four twelfths, use an age factor of 2.5 because growth, thermoregulation, and play dwarf adult maintenance. Activity then multiplies that life-stage figure: sedentary is 1.2 for a typical neutered indoor cat, moderate is 1.4 for a mixed indoor-outdoor day, active is 1.6 for a working or outdoor cat, and very_active is 1.8 for a highly athletic animal. calories_per_day is the half-up rounded product of RER times age_factor times activity_factor, reported in kilocalories per twenty-four hours.
Input contract, response shape, and error behaviour
A six-month kitten of 1.2 kg at moderate activity is still in the kitten band (age factor 2.0) and therefore needs a larger multiple of its smaller rest figure. POST a JSON body with three required fields. weight_kg is the cat's body mass in kilograms (aliases weight, kg, mass_kg) and must be a finite positive number no greater than forty; a newborn kitten of one hundred grams is legal, a zero or negative paste is not. age_years is age in years (aliases age, years), a finite number in the closed interval from zero to thirty; use a fraction for kittens so that 0.25 is three months and 0.5 is six months. activity is one of the closed enum sedentary, moderate, active, or very_active (aliases activity_level, level). Each numeric field may arrive as a JSON number or as a numeric string. Missing fields, empty strings, non-finite values, a weight that is not positive, a weight above forty kilograms, a negative age, an age above thirty, and an activity string outside the enum fail with invalid_input naming the field. Those failures are not billed. On success the body echoes the cleaned weight_kg, age_years, and activity, publishes life_stage as kitten, adult, or senior, reports rer_kcal as resting energy rounded to two decimals, reports age_factor and activity_factor as the two multipliers, reports mer_factor as their product, and returns calories_per_day as the integer kilocalorie target. formula restates RER equals 70 times W to the 0.75 and MER equals RER times age_factor times activity_factor. Example: weight_kg 4.5, age_years 3, activity sedentary is an adult indoor cat whose resting energy is about two hundred and sixteen kilocalories and whose daily target is two hundred and sixty kilocalories. Pair the integer calories_per_day with the metabolizable energy printed on the food, in kcal per can or per cup, to turn a daily target into a feeding amount; this endpoint does not parse food labels or score body condition.
Where a cat calorie calculator earns its keep
Exam-prep generators and student nutrition katas pin a known indoor adult and a known kitten plus the invalid_input path for a non-positive weight so a buggy grader cannot accept a negative energy figure. Keep the three inputs honest, pin calories_per_day in tests, and you get a reproducible daily kilocalorie target for homework, LMS plugins, shelter spreadsheets, and feeding apps.
Integration use cases
Shelter and boarding batch estimates
A spreadsheet of weights, ages, and a coarse activity flag becomes a column of calories_per_day figures without opening a veterinary nutrition package for each row.
Technical questions
How does age change the calorie target?
Age selects the life-stage factor. Under four months the factor is 2.5, from four months to one year it is 2.0, from one year to seven years it is 1.0, and from seven years it is 0.9. life_stage in the response is kitten, adult, or senior.
What do the activity levels mean?
sedentary (1.2) is a typical neutered indoor cat. moderate (1.4) is mixed indoor-outdoor. active (1.6) is outdoor or working. very_active (1.8) is a highly athletic cat. The enum is closed; any other string is invalid_input.
What does the cat calorie calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.