Enter your kitten's breed, current age, and weight. The calculator projects adult cat size using breed-specific growth curves — including the slow-growth large breeds (Maine Coon, Ragdoll, Norwegian Forest) that don't reach full size until 2–3 years old. Free, no ads, no data sales.
Track this over time, not just once. Kittens have wider variation than puppies because most are mixed lineage. Re-weigh every 2 weeks; the curve converges fast. Open DenLumen to log each weigh-in and see the trajectory.
| Age | Domestic shorthair | Maine Coon | Ragdoll |
|---|---|---|---|
| 4 weeks | 1 lb | 1.5 lb | 1.3 lb |
| 8 weeks | 2 lb | 2.5 lb | 2.4 lb |
| 12 weeks | 3 lb | 4 lb | 3.7 lb |
| 16 weeks | 4–5 lb | 6 lb | 5.5 lb |
| 6 months | 6 lb | 9 lb | 8 lb |
| 9 months | 7–8 lb | 12 lb | 10 lb |
| 12 months | 8–10 lb | 14 lb | 13 lb |
| 24 months | full | 16–18 lb | 15–17 lb |
| 36 months | full | 18–25 lb | full |
Most domestic cats (shorthair, longhair, common mixes) reach about 75% of adult weight by 6 months and 95%+ by 12 months. Maine Coons, Norwegian Forest Cats, Ragdolls, Savannahs, Siberians, and a few other large breeds have a fundamentally different growth pattern: they finish skeletal growth around the same time as domestics, but continue building muscle mass and frame width for another 2–3 years. A Maine Coon at 12 months can weigh 13–15 lb but still gain another 4–6 lb of mass by age 3.
The calculator accounts for this — it uses different curves per breed group so a 6-month-old Maine Coon isn't projected to the breed's full adult size as if it were a domestic shorthair.
A healthy kitten gains roughly 1 lb per month for the first 6 months. Typical milestones: 1 lb at 4 weeks, 2 lb at 8 weeks, 3 lb at 12 weeks, 4–5 lb at 16 weeks. By 6 months most domestic kittens reach ~75% of adult weight; by 12 months they're full size. Large breeds (Maine Coon, Norwegian Forest, Ragdoll) keep growing until 24–36 months.
Most domestic cats finish growing by 12 months. Larger-breed cats (Maine Coon, Ragdoll, Norwegian Forest Cat, Savannah, Siberian) continue gaining size and muscle mass until 18–36 months.
A kitten that's consistently below 50% of typical weight for age, or that fails to gain at least 50–100 g (2–4 oz) per week before 4 months, warrants a vet check. Common causes: parasites (deworm), insufficient calorie intake, or congenital issues.
One projection has wide uncertainty for cats. A series converges fast — DenLumen logs every weigh-in and charts the curve with breed-specific bands.
Open DenLumenStep-by-step instructions for the features on this page: