Just how old is Fido or Fluffy in human years? There are lots of answers to this question. All are based on arbitrary information, and many websites and publications make dubious assumptions. None of these ideas have been proven, and you will likely find different answers depending on which reference you use.

An example of a very general (and likely inaccurate) measure of dog or cat years to human years is the ‚ÄúPets Age Faster than Humans‚ÄĚ poster found at the American Veterinary Medical Association website. But if you want a true understanding of the true age of your pet, where do you turn?

The math

Let’s start with cats. Many of references assume that a human can live to 100 years and a cat to 20 years and that a cat is mature at 1 year of age. Thus, the time spanning birth to one year in cats is equivalent to birth to 18 years for humans; in other words, growth and puberty to adulthood.

After 1 year of age, a cat’s age to 20 years is equated to a person living until 100 years, which means that after age 1, each year in a cat’s life is approximately equivalent to 4 years (actually 4.3 years if you do the math). For example, a 15-year-old cat would be approximately 78 human years old (cat year 1 = 18 human years and then 4.3 human years for 14 more cat years, which is 60.2 human years; 60.2 + 18 = 78.2 human years).

This is similar to a table provided in the American Animal Hospital Association/American Association of Feline Practitioners Life stage Guidelines, but with some subtle differences. The assumption that cats live to 20 years and humans live to 100 years is a very broad assumption. Additionally, this method assumes that aging occurs in a linear fashion; that is, each year is the same as every other year, which we know is not true from a metabolic and physiologic perspective.

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The cat bible

Another method of calculation comes from the book, The Cat Bible, by Tracie Hatchner, which provides the following:

  • 1-month-old kitten = 6-month-old human baby
  • 3-month-old kitten = 4-year-old child
  • 6-month-old kitten = 10 human years old
  • 8-month-old kitten = 15-year-old human
  • A 1-year-old cat has reached adulthood, the equivalent of 18 human years
  • 2 human years = 24 cat years
  • 4 human years = 35 cat years
  • 6 human years = 42 cat years
  • 8 human years = 50 cat years
  • 10 human years = 60 cat years
  • 12 human years = 70 cat years
  • 14 human years = 80 cat years
  • 16 human years = 84 cat years

This table does not assume a direct linear relationship between each year, which is a more accurate measurement of true age.

Aug 24, 2013

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