How the Kitten Weight Calculator Works
This kitten weight calculator answers the question every new owner asks: is my kitten the right weight? It compares your kitten’s weight against veterinary growth ranges by age and sex — because male kittens run heavier than females — and flags whether it is below, within, or above the healthy range. The simplest rule of thumb is that a kitten weighs about one pound per month of age up to around five months, so an 8-week-old kitten weighs roughly 2 lb (about 0.9 kg). To predict the adult weight, it uses the standard formula adult weight ≈ (current weight ÷ age in weeks) × 32, with kittens reaching about half their adult size by 16 weeks and males finishing around 10% heavier. The tool also converts the full kitten weight chart into grams, kilograms, ounces and pounds, estimates age from weight, and tracks daily gain — where a healthy young kitten adds about 7 to 14 grams a day.
The five tools cover a weight check by age and sex, an adult-weight predictor, a weight chart in every unit, age from weight, and a daily-gain tracker.
Kitten Weight Chart by Age (Male & Female)
This kitten weight chart shows healthy ranges from birth to 12 months, split by sex. Males are typically a little heavier than females at every age. Use it to check your kitten against its age, in grams, pounds and kilograms.
| Age |
Female |
Male |
Approx. (kg) |
| Birth |
2.5–3.5 oz |
3–4.5 oz |
0.07–0.13 kg |
| 4 weeks (1 mo) |
11 oz–1 lb |
13 oz–1.1 lb |
0.31–0.5 kg |
| 8 weeks (2 mo) |
1.3–1.8 lb |
1.5–2.2 lb |
0.6–1.0 kg |
| 12 weeks (3 mo) |
2.2–3 lb |
2.5–3.8 lb |
1.0–1.7 kg |
| 4 months |
3–4.5 lb |
3.5–5.5 lb |
1.4–2.5 kg |
| 5 months |
4–5.5 lb |
4.5–6.5 lb |
1.8–3.0 kg |
| 6 months |
5–7 lb |
6–8 lb |
2.3–3.6 kg |
| 12 months |
7.5–10 lb |
8.5–12 lb |
3.4–5.4 kg |
Large breeds like Maine Coon and Ragdoll run well above these numbers and keep growing to 18–24 months. The Weight Chart tab gives your kitten’s exact range in grams, oz, lb or kg.
How Much Should My Kitten Weigh?
For a standard domestic kitten, the easiest guide is the one pound per month rule: about 1 lb at 4 weeks, 2 lb at 8 weeks, 3 lb at 12 weeks, climbing by roughly a pound a month until five to six months, then slowing toward the adult weight by about a year. In grams, a newborn is 70–130 g, a 4-week kitten around 400 g, an 8-week kitten about 900 g, and a 12-week kitten roughly 1.4 kg. Sex matters: by adulthood a female domestic cat usually weighs 7.5–10 lb and a male 8.5–12 lb. Remember these are averages — a healthy kitten tracks a steady upward curve rather than landing on an exact figure, so a single reading a little high or low is rarely a worry on its own.
How to Predict Your Kitten’s Adult Weight
The most widely used estimate is the formula adult weight ≈ (current weight ÷ age in weeks) × 32. A kitten that weighs 4 lb at 16 weeks projects to roughly 8 lb as an adult, which fits the related rule that a kitten is about half its adult weight at 16 weeks. You can also use age multipliers: multiply the weight at 8 weeks by about 4–4.5, at 12 weeks by 3, at 16 weeks by 2.25–2.5, and at 6 months by 1.2–1.3. All of these are rough — the old “double the weight at 4 months” shortcut is often inaccurate, especially for large breeds and males, which keep growing well past a year. Breed is the biggest factor: a Maine Coon or Ragdoll can finish at two to three times the weight of a petite Siamese, so always weigh the formula against the typical range for the breed.
How to Weigh a Kitten (No Pet Scale Needed)
The most accurate way is a digital kitchen scale that reads in grams: put a small bowl or box on it, press tare to zero it out, then set the kitten inside — grams let you see even a few days’ growth. For a larger kitten with no kitchen scale, use the bathroom-scale method owners recommend: weigh yourself, then weigh yourself holding the kitten, and subtract. Do it on a hard floor within a short window for the most consistent reading. Weigh at the same time of day, ideally before a meal, and record each figure so you can watch the trend. For very young or bottle-fed kittens, daily weigh-ins are worth it — a day or two of no gain is an early warning worth acting on.
Frequently Asked Questions
How much should an 8-week-old kitten weigh?
An 8-week-old kitten usually weighs about 2 lb (roughly 0.9 kg) — around 1.3 to 1.8 lb for females and 1.5 to 2.2 lb for males. The rule of thumb is about one pound per month of age up to five months.
How old is a kitten that weighs 350 grams?
A kitten weighing about 350 grams is roughly 3 to 4 weeks (about one month) old, since kittens weigh around 280 to 450 g over that span. Confirm with physical signs like teeth and eye colour, as weight alone can be off by a week or two.
How do I know how much my kitten will weigh as an adult?
Use the formula adult weight = (current weight / age in weeks) x 32, or note that a kitten is about half its adult weight at 16 weeks. Breed and sex matter most — males finish about 10% heavier, and large breeds keep growing past a year.
How much weight should a kitten gain per day?
A healthy young kitten gains about 7 to 14 grams a day, or roughly 100 grams a week, in the first few months. Daily readings bounce, so watch the weekly trend. A kitten that stops gaining or loses weight needs a vet promptly.
What is the 3-3-3 rule for kittens?
The 3-3-3 rule is about settling in, not weight: roughly 3 days to decompress in a new home, 3 weeks to learn the routine, and 3 months to feel fully at home. For weight, use the one-pound-per-month rule of thumb instead.
Is 7 lb too skinny for a cat?
Not necessarily. Many adult cats, especially small-framed females and slender breeds like the Siamese, are perfectly healthy at 7 lb. What matters is body condition — whether you can feel the ribs under a thin layer of fat and see a waist — not the number alone.
How do I weigh my cat without a scale at the vet?
Weigh yourself on a bathroom scale, then weigh yourself holding the cat and subtract the difference. For kittens, a digital kitchen scale in grams with a bowl tared to zero is more precise and shows small daily gains.
Do male kittens weigh more than female kittens?
Yes. Males are often slightly heavier even as kittens and typically finish about 10% heavier than females as adults, with a larger frame. The calculator and chart above give separate ranges for each sex.
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PetCalculatorHub Editorial Team
The weight ranges here are built from standard veterinary and rescue growth charts (about a pound a month, with separate male and female ranges), and the adult-weight projection uses the widely cited (weight ÷ age in weeks) × 32 formula. Every kitten grows at its own rate, so these are guides, not diagnoses. Weigh on the same gram scale over time, feed a growth-formula kitten food, and see your veterinarian for vaccinations, deworming and any kitten whose weight stalls or drops.
Last updated: October 2026
