Most house cats do the majority of their growing in the first year and are usually close to full size by about 12–18 months, though some larger breeds keep growing slowly until 2–4 years old.

Main growth timeline

  • Newborn to 6 months: Fastest growth; kittens often reach around 75% of their adult size by 6 months.
  • 6–12 months: Growth slows; most average-sized cats are near their adult length and height by their first birthday.
  • 12–18 months: Many cats finish filling out in muscle and weight during this period and are considered fully grown.
  • 2–4 years (large breeds): Big breeds like Maine Coons and Ragdolls can keep growing and filling out until around 3–4 years old.

Factors that change how long cats grow

  • Breed :
    • Typical domestic shorthair/most mixed-breed cats: stop growing around 12–18 months.
* Large breeds (Maine Coon, Ragdoll, Norwegian Forest): may grow until 2–4 years.
  • Sex and hormones:
    • Males often grow a bit longer and end up larger than females.
* Spay/neuter can delay growth plate closure slightly, so some fixed cats grow a bit longer and taller before they stop.
  • Nutrition and health:
    • Kittens with good-quality, appropriate kitten food grow more steadily and reach their genetic potential size.
* Illness or poor diet in kittenhood can slow growth or change the normal pattern.

How to tell your cat is done growing

  • Height and length stop changing: You no longer see your cat getting noticeably taller or longer over a few months.
  • Weight stabilizes: The number on the scale levels out; after this, changes tend to be fat gain or loss, not actual growth.
  • Adult body shape: Face and body look more “adult” and less lanky; muscles are more developed, especially in males.

Quick FAQ

  • How long do most cats grow?
    • Around 1–1.5 years for average cats; up to 2–4 years for big breeds.
  • Is my 1-year-old cat still a kitten?
    • Behavior can still be kitten-like, but physically many are at or near full size at 12 months, with a bit of filling out left to do.
  • Should I worry if my cat is small?
    • Some cats are naturally petite; what matters more is steady growth in kittenhood and a healthy body condition as an adult.

Information gathered from public forums or data available on the internet and portrayed here.