When do kittens reach full size?
Written by
Victoria Hayes
Reviewed by
Prof. Edward Clarke, Ph.D.Full physical maturity in kittens can occur at different rates, depending on genetics (principally breed) and nutrition. Most domestic shorthair breeds grow to full size by 9 to 12 months of age. Large breeds, such as Maine Coons, can take 15-18 months to reach their full size. Providing the right nutrition and care for kittens in this period helps avoid future clumsiness or serious long-term problems.
Breed Differences
- Small breeds: Siamese reach full size earliest at 9-10 months
- Medium breeds: Domestic shorthairs finish at 12 months
- Large breeds: Maine Coons and Ragdolls grow until 15-18 months
- Giant breeds: Savannahs may develop until 24 months
Nutritional Requirements
- High-protein diets support muscle development throughout growth
- Calcium-rich foods strengthen bones during rapid growth phases
- Adjust portions monthly based on weight gain patterns
- Continue kitten-specific formulas until growth plates close
Health Monitoring
- Weigh weekly using digital kitchen scales
- Track body condition scores monthly with vet guidance
- Check for growth plate closure via x-rays after 12 months
- Monitor joint health for large breed kittens
Weekly weight tracking helps gauge the kittens' development. Weigh each kitten with digital scales every Tuesday morning before feeding, and record the weights in pounds and kilograms. A healthy kitten will gain between half an ounce and an ounce, or 14−28 g, each day until it is six months of age. If the scales remain the same or decrease, take them to the vet immediately.
Nutritional Physique: Kittens have high nutritional needs. Most kittens should continue to eat high calorific food up to 12 months; larger breeds should eat specialist formulae up to 18 months. I recommend food from brands like Royal Canin Size Health Nutrition which are formulated to support controlled growth rates.
Look for the signs of growth completion like stable weight over three months and decreased interest in food. An adult cat has noticeably prominent cheekbones and a more muscular definition. Your veterinarian looks for conclusive evidence through X-ray and physical exam. Gradually transition to adult food over the course of two weeks.
This stage of growth lays the foundation for lifelong health. Adequate nutrition helps prevent developmental bone disease. Routine exams help catch any problems at an early stage. Your watchful care is the best way to help your kitten become a happy, healthy, and well-nourished adult cat with the ideal body condition.
Read the full article: Kitten Developmental Milestones Explained Simply
