Your cat's teeth can provide clues. Kittens have sharp needle teeth. Senior cats show wear, tartar, and missing teeth.
Shiny, sleek coats signal youth and health. Dull, thinning coats indicate senior age.
Kittens and young cats are energetic. Middle-aged and senior cats are more sedentary.
Kittens and young cats have firm muscle tone. Older cats have looser muscle tone and thinner frames.
Kittens are under 1 year. Prime adulthood is 1-10 years. Senior stage starts around 11 years.
Your vet can help estimate age based on dental exams, condition, and medical records if available.
Some breeds like Siamese live longer so may seem younger than their calendar age suggests.