Kitten Age Estimator (Weight, Eyes, Teeth) & Milestone Planner
Estimate a found or rescued kitten's age from its weight and developmental signs — eyes, ears, walking, teeth — then get the expected weight for that age, feeding frequency, litter training, the vaccination and deworming schedule and the spay/neuter window.
How it works
age (weeks) ≈ (weight − 100 g) ÷ 100 g/week up to 8 weeks, then ≈ 1 lb (450 g) per month; cross-checked against eye, tooth and mobility milestones
Kittens grow on a remarkably steady schedule — roughly a hundred grams a week for the first two months and about a pound a month after that — so weight gives a first guess at age, but a sick or orphaned kitten can be badly underweight, so the physical milestones that do not depend on nutrition are the tie-breakers: eyes open at about ten days and stay blue until six or seven weeks, baby incisors erupt in the third week and canines in the fourth, and the whole deciduous set is in by six weeks. Combining the ranges narrows the estimate, and once age is known the rest follows — how often to feed, when the litter tray can replace stimulation, and when the vaccine series and neutering should fall.
Worked example
A 450 g kitten with blue eyes, tiny incisors and a wobbly walk: weight suggests 3.5 weeks, and the eyes (2–7), teeth (2.5–4) and gait (2–4) agree on 2.5–4 weeks, so about 3.5 weeks. The expected weight is ≈ 450 g, so it is on track; feed every 5–6 hours introducing gruel, start a shallow litter tray, and plan the first FVRCP vaccine in about 3.5 weeks.
Frequently asked questions
I found a kitten with its eyes closed — what first?
Warmth before food: a chilled kitten cannot digest. Warm it gradually to normal body temperature, then feed kitten milk replacer (never cow's milk) every 2–3 hours, stimulate it to toilet, and have a vet check it within a day.
When can it be rehomed?
Not before 8 weeks, ideally 10–12: kittens learn bite inhibition and litter habits from their mother and littermates in weeks 6–10, and early separation is linked to behaviour problems.
Related calculators
General veterinary guidance and rules of thumb (WSAVA / AAHA nutrition and reproduction references). Every animal differs — confirm feeding amounts, pregnancy timing and any concern with your veterinarian, especially for kittens, puppies, seniors and animals with medical conditions.