Cat Calculators
Feline-specific biology: age conversion, body condition, caloric needs, water turnover, growth projections, and safe dosage ranges. Every medication tool carries a veterinary review credit and a clear 'confirm with your vet' disclaimer.
Feline calculations share a structure with the dog tools but not the numbers. Cats age on a different curve, score body condition by their own standards, and differ in water turnover and calorie density per kilogram, so species-specific conversion matters throughout. Start with the age or body-condition tool for a baseline, then move to the calorie and water-intake estimates when planning a diet change or a feeding routine for a kitten or a senior cat. Growth projection works best on a kitten with a known breed or a measured growth history, not a single weight taken on one day.
Each dosage calculator carries a veterinary review credit and a clear instruction to confirm the number with your vet, because dosing depends on the drug, the formulation, and the reason for giving it, not weight alone. The chocolate toxicity tool shows how estimated exposure scales with body weight, which explains why a small quantity is a proportionally bigger deal for a small cat. Age-conversion and quality-of-life tools describe population patterns rather than individual outcomes, so treat them as a way to frame a conversation at the clinic. Most visitors arrive with one specific number to check between appointments.
Start here
Three picks, one per job: start with the one that matches what you came to calculate.
- Size a dose in milligrams or tablets: Cat Benadryl Dosage Calculator: milligram-per-kilogram arithmetic with the published feline bands printed beside it
- Triage a chocolate exposure: Cat Chocolate Toxicity Calculator: puts the amount eaten against Merck's risk bands for this cat's exact weight
- Set a daily feeding target: Cat Calorie Calculator: resting energy times life-stage multipliers, with treats and cups already accounted for
Calculators
Age and growth
Weight, food and water
Prescription dosing
Supplements, emergencies and welfare
Guides & explainers
Each guide goes deep on the science behind one or two calculators and links straight into them.
- Feline CKD Subcutaneous Fluid Therapy & Hydration Guide
- Cat Age Quiz (interactive)
- How to Tell Your Cat's Age in Human Years
- Is My Cat Overweight? Understanding Cat BMI
- How Big Do Kittens Get? Growth Milestones by Breed
Which tool do I need?
| If you need to… | Use | Why this one |
|---|---|---|
| need a human-year equivalent and the screening schedule | Cat Age Calculator | the 15 / 9 / +4 curve with the life stage attached |
| project how large a kitten will grow | How Big Will My Cat Get Calculator | growth-fraction projection with a large-breed clock shift |
| turn a body condition score into fat and lean mass | Cat BMI Calculator | nine-point score mapped to body-fat bands and an ideal weight |
| work out daily calories including treats | Cat Calorie Calculator | resting energy with Merck multipliers and a cup conversion |
| find out whether this cat is drinking too much | Cat Water Intake Calculator | 60 mL/kg need minus food moisture, with the polydipsia line beside it |
| put a number on how a hard week is going | Cat Quality of Life Calculator | seven domains summed straight, with flags on any row below 5 |
| work out how urgent a chocolate exposure is | Cat Chocolate Toxicity Calculator | grams eaten converted to mg/kg against Merck's stepped risk bands |
| turn a prescription into capsules and a course total | Cephalexin for Cats Dosage Calculator | published feline rate bands bracketing the prescribed figure |
| size an antihistamine dose for this cat's weight | Cat Benadryl Dosage Calculator | AAHA and Merck bands side by side, with tablet fractions |
| convert a meloxicam rate into syringe millilitres | Metacam Dosage Calculator for Cats | bottle-strength conversion with the feline label rate as default |
| set an omega-3 target from EPA and DHA content | Fish Oil Dosage Calculator for Cats | 50 to 220 mg/kg/day range with the Bauer caution line printed beside it |
Cat: common questions
How do I convert my cat's age to human years?
Use the 15 / 9 / +4 curve: the first year counts as about 15 human years, the second adds 9, and each year after that adds roughly 4. The age calculator attaches the AAHA life stage to that figure so the screening schedule follows with it.
Is the ×7 rule for cat age accurate?
No. It draws a straight line, so it undersells a one-year-old at 7 human years and inflates a fifteen-year-old to 105. The piecewise curve used here lands those same ages at 15 and 76.
How many calories should an adult cat eat a day?
Start from resting energy (70 times weight in kilograms to the power 0.75), then apply the life-stage multiplier: 1.2 for a neutered adult, 1.4 intact, 1.0 obesity-prone. A 4.5 kg neutered adult lands near 262 kcal before treats, and treats stay at or below 10% of the total.
When should I call the vet about chocolate?
Call as soon as the estimate reaches the mild-signs band around 20 mg/kg, and call earlier if you are unsure. Signs take 6 to 12 hours to appear and decontamination works best within the first two hours, so have the chocolate type, grams eaten, cat's weight and time of ingestion ready.
What water intake is too much for a cat?
Sustained intake above 100 mL per kg per day (about 450 mL for a 4.5 kg cat) is the level veterinary guidance treats as polydipsia. Measure for three days with the food's moisture counted before you judge the bowl.
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