Cat calorie calculator
Work out a cat's daily energy need: resting energy is 70 times weight in kilograms to the power 0.75, and a neutered indoor adult of 4.5 kg then gets a maintenance factor of 1.2. Kittens use 2.5. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Weight
- 4.5
- Age
- Adult
- Activity
- Indoor
- Weight (kg)
- 4.5
- Weight unit
- Kg
- Mer factor
- 1.2
- Rer kcal
- 216.2755501102
House cats, barn cats, and growing kittens do not share one daily calorie number. Body size sets the resting energy requirement, while life stage, neuter status, and how much the animal actually moves decide the multiplier that turns rest into maintenance. This cat calorie calculator takes a positive body weight in kilograms or pounds, a life stage of kitten, adult, or senior, a neuter flag, and an indoor, moderate, or outdoor activity class. It returns resting energy in kilocalories, the published-style maintenance factor, and the daily MER in kilocalories per day. The algorithm is the exponential veterinary identity RER equals seventy times body weight in kilograms to the power three quarters, then MER equals RER times the factor.
How a cat's daily calorie requirement is calculated
Veterinary nutrition teaching almost always starts from resting energy requirement, the energy a mammal of a given mass would expend at rest in a thermoneutral room. For cats the exponential form is preferred over the old linear thirty-times-weight-plus-seventy rule, because the exponential tracks small and large bodies more honestly: RER in kilocalories per day equals seventy times body weight in kilograms raised to the power three quarters. Maintenance energy requirement then scales that rest figure by a published factor that depends on growth, gonadal status, and lifestyle.
Growing kittens are assigned two point five times RER regardless of indoor or outdoor life, because tissue accretion dominates the budget. Neutered adult house cats typically sit at one point two times RER; intact adults need about one point four. Moderate indoor-outdoor adults rise to one point four if neutered and one point six if intact.
Outdoor or very active adults use one point six and one point eight. Senior cats usually need less than comparable adults: indoor neutered seniors use one point one, indoor intact seniors one point two, with the same activity steps of two tenths above those floors. Pounds convert with the international avoirdupois kilogram, zero point four five three five nine two three seven, before the power is taken, so a ten-pound indoor neutered adult is not treated as a ten-kilogram cat.
Treat the number as a planning estimate for label math and portion drafts, not as a prescription that replaces a veterinarian who can see body condition, disease, and the actual food.
Where a cat calorie calculator earns its keep
Rescue intake desks and foster coordinators need a repeatable daily kilocalorie target when a new adult arrives without a feeding history, and they need the kitten factor when a litter is still growing. Shelter software and clinic worksheets can call the same parse module from a form or from a batch job without standing up a nutrition suite. Do not use the figure as a crash diet: weight-loss protocols for obese cats are slower and should be supervised, because hepatic lipidosis is a real risk when intake is slashed.
Re-weigh on the same scale, watch body-condition score, and move the activity class when an indoor cat starts outdoor access or when a senior becomes sedentary.
What you can do with it
Set a starting daily portion from the bag label
Compute kcal per day for an indoor neutered adult, then divide by the food's metabolizable energy per cup or per gram to draft a feeding amount.
Scale kitten versus adult rations in a foster home
Switch age to kitten to apply the 2.5× RER growth factor, then back to adult after one year so the same weight is not overfed.
Adjust calories when lifestyle or neuter status changes
Recalculate after spay or neuter, or when an indoor cat becomes outdoor-access, so the MER factor tracks the new energy demand.
FAQ
How do I calculate a cat's daily calories?
Send a positive weight plus age (kitten, adult, or senior), neutered, and activity (indoor, moderate, or outdoor).
What formula does the cat calorie calculator use?
Resting energy is 70 × (body weight in kilograms)^0.75. Maintenance energy is that RER multiplied by a WSAVA-style factor for life stage, neuter status, and activity.
What happens if weight is zero or negative?
Weight must be a finite positive number; missing, zero, negative, or non-numeric values are rejected and are not billed.
Should I use kilograms or pounds?
Send lb, lbs, pound, or pounds to convert with the international avoirdupois factor before the power is taken.
Why do kittens need more calories?
Growing kittens are assigned 2.5 times their resting energy, whatever their activity, because growth adds to their basic needs. A neutered indoor adult uses a much lower factor of 1.2.
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/cat-calorie \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"weight":4.5,"age":"adult","neutered":true,"activity":"indoor"}'const res = await fetch("https://api.kit.forhosting.com/bio/cat-calorie", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"weight": 4.5,
"age": "adult",
"neutered": true,
"activity": "indoor"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/bio/cat-calorie",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"weight": 4.5,
"age": "adult",
"neutered": true,
"activity": "indoor"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/bio/cat-calorie", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"weight":4.5,"age":"adult","neutered":true,"activity":"indoor"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"weight":4.5,"age":"adult","neutered":true,"activity":"indoor"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/bio/cat-calorie", 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": 4.5,
"age": "adult",
"neutered": true,
"activity": "indoor"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "bio.cat_calorie",
"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.
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
Weight that is missing, zero, negative, or not a finite number fails with invalid_input and is not billed.
How a cat's daily calorie requirement is calculated
The endpoint reports both RER and MER, echoes the normalized inputs, and restates the identity in a formula string.
Input contract, response fields, and validation errors
Missing or unknown age, neuter, or activity values fail the same way and name the field. Example: four point five kilograms, adult, neutered, indoor uses factor one point two on seventy times four point five to the three-quarters, which is the classic indoor-pet case. POST a JSON body with four required fields. weight is a finite positive number in the unit given by optional weight_unit, which defaults to kilogram and also accepts pound and the usual aliases kilogram, kilograms, lb, lbs, pound, and pounds. After conversion the mass must fall between one tenth of a kilogram and fifty kilograms so a decimal typo cannot explode the power. age is the life stage kitten, adult, or senior; aliases life_stage, stage, and age_group are accepted, and a numeric age_years value maps under one year to kitten, under eleven years to adult, and eleven or more to senior. neutered is a boolean, or the strings neutered, spayed, desexed, intact, and the usual yes or no forms. activity is indoor, moderate, or outdoor, with aliases such as sedentary, indoor-outdoor, and active. Each numeric field may arrive as a JSON number or as a numeric string. Missing weight, zero, a negative, NaN, or a non-numeric string fails with invalid_input naming weight and stating that it must be a positive number; those failures are not billed. On success the body echoes weight, weight_kg, weight_unit, age, neutered, and activity, then returns mer_factor, rer_kcal, kcal_per_day as the primary daily figure, calories as the same daily figure for clients that look for that name, and a formula string. Successful API calls use prepaid KIT balance at the published $0.002 base price per item.
Where a cat calorie calculator earns its keep
Boutique and veterinary-aisle brands publish metabolizable energy on the bag; dividing this endpoint's kcal_per_day by the food's kilocalories per cup or per gram turns an abstract MER into a starting portion, which is the search intent behind cat calorie calculator and daily calories for cat food. Pair the daily kilocalories with the actual metabolizable energy of the diet you feed; this endpoint does not read a bag label and does not diagnose disease.
Technical questions
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.