Cats are usually considered full grown between 12 and 18 months old, but some larger breeds can keep growing for several years. Most kittens look “adult” by about 6–12 months, even though their body is still filling out inside.

Quick Scoop

  • Most typical house cats reach adult size at about 1 year old.
  • Growth often slows after 6 months but continues more gradually until 12–18 months.
  • Female cats often finish growing a bit earlier (around 10–12 months) than males, which may grow up to around 18 months.
  • Big breeds like Maine Coons can keep growing until 3–5 years of age, so they’re “late bloomers.”

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