Cat beside a notebook for the cat years to human years calculation method

Cat years made simple

How Kitten Years Calculates Cat Age

Cat age conversion is a helpful estimate, not a medical measurement. Here is the simple method behind the calculator and charts.

The cat age formula

Kitten Years uses the common 15-9-4 cat age method. The first cat year is estimated at about 15 human years. The second cat year brings the estimate to about 24 human years. After that, each additional cat year adds about four human years.

For kitten months, the calculator uses a smooth month-by-month estimate so a kitten under one year old can still receive a result.

The life stages used on this site

For a clear public-facing experience, Kitten Years uses five simple life stages: kitten, young adult, mature adult, senior, and super senior. Veterinary and cat-care organizations may use slightly different stage names, so the site explains this on the Cat Life Stages page.

Sources and care references

Kitten Years is written as general educational information and should not replace a veterinarian. These sources shaped the age method, life-stage language, and care reminders:

Plain-language age pages

Age pages are intentionally written in plain language. The goal is to answer the age question quickly, then help readers understand what that age can mean in normal daily life.