The Secret History Behind Cat Years


The concept of “cat years” refers to the idea that cats age faster than humans, so each year of a cat’s life is said to be equivalent to 7 human years. The practice of calculating a cat’s age in “cat years” likely arose as a way for owners to understand the aging process in their feline companions, whose average lifespan of 12-18 years is shorter than the human average of around 70 years. This article will explore the origins of this popular concept, examine how accurate the 7:1 ratio really is, and look at how the idea of “cat years” is understood today.

What are ‘cat years’?

The concept of ‘cat years’ refers to the idea that cats age faster than humans in the first few years of life. It’s commonly said that the first year of a cat’s life is equal to about 15 human years. After the first year, each additional year in a cat’s life is said to be equal to about 4 human years.

This 7:1 ratio (7 cat years for every 1 human year) is meant to help compare the aging process in cats versus humans. It accounts for the fact that cats reach sexual maturity around 1 year old, whereas humans don’t reach it until around 15 years old. Cats also tend to live shorter lifespans of 15-20 years, versus 70-90 years for humans.

So the 7:1 ratio aims to adjust for those differences and allow us to understand a cat’s relative age compared to a human’s in years we can more easily comprehend. Of course it’s not an exact science, but it provides a rough approximation to conceptualize a cat’s age.

When did the concept first appear?

The earliest known reference to calculating cat years comes from a 1953 issue of Popular Mechanics magazine. In an article about pet health, the author notes that “veterinarians have worked out a set of age ratios based on the normal life expectancies of animals. A 1-year-old dog equals a 14-year-old boy, and a 1-year-old cat equals a 15-year-old boy.” This suggests the concept of cat years had already been around for some time in veterinary medicine by the early 1950s.

Throughout the 1950s and 1960s, the idea of cat years continued to spread in popular culture. Sources from the era often used a 7:1 ratio, calculating that for every 7 human years, a cat aged 1 year. Cats were said to reach maturity around 2 years old or 14 human years. By the 1970s, cat years were commonly referenced in books, magazines, and newspapers when discussing the age and life stages of cats.

While the precise origins are uncertain, the rough concept of cat years dates back at least 70 years. Early veterinarians appear to have devised the ratios based on life expectancy, to help people understand the aging process in their pets.

Who popularized cat years?

The concept of cat years was popularized in the 1950s by Dr. Mark Morris Sr., an American veterinarian who developed prescription cat food. Dr. Morris created the cat age to human age ratio of 1 year to 7 human years in order to help cat owners understand their pets’ life stages and determine their nutritional needs (See reference).

This 7:1 ratio was a useful guideline at the time, as cats were living much shorter lifespans on average compared to today. Dr. Morris’ cat food allowed cats to live longer, healthier lives. His innovative feline diet and the catchy concept of “cat years” became popular among cat owners and veterinarians in the 1950s.

Though not scientifically exact, the 7:1 ratio gave cat owners an easy way to understand the different life stages and aging process of their pets. Dr. Morris Sr. helped popularize the idea through his cat food products, veterinary practice, and advocacy. While not as commonly used today, “cat years” persists as a cultural concept thanks to its effectiveness as a communication tool first promoted in the 1950s.

Do cat years accurately reflect aging?

Recent scientific studies give us a better understanding of the aging process in cats. According to a 2021 review, cats are generally not recognized as a model for aging research, mainly due to limited knowledge and appreciation of feline aging patterns (Ladiges et al.). However, increased research focused on aging in cats can provide useful insights.

A 2022 study analyzed owner observations and clinical findings for 1,114 cats ages 4 to 20 years. The results showed the prevalence of common age-related conditions increased starting around age 11. Most cats over 15 years old had at least one age-related condition. This suggests the aging process accelerates in the second decade of life (Dowgray).

Estimates of mean lifespan from studies range between 13-20 years, with most around 15 years. At least one study found indoor cats live significantly longer compared to outdoor cats (Wikipedia). Overall, research indicates cat years do not accurately reflect the aging process and lifespan.

Why use cat years?

People use cat years to more easily compare cats’ ages to human ages. Since cats mature much faster than humans in their first couple years of life, assigning “cat years” allows us to better understand where a cat is developmentally. For example, at 1 year old a cat reaches the maturity of a 15 year old human, while a 2 year old cat is around 24 in “cat years.” This faster aging early on means a 1 or 2 year old cat would be considered middle aged, while a 1 or 2 year old human would still be a young child. Using cat years gives us a way to wrap our heads around how quickly our feline companions grow up. Cat years also help us determine a cat’s life stage and approximate life expectancy. Though not scientifically precise, cat years provide a general guideline for understanding a cat’s age relative to a human’s [1].

How accurate is the 7:1 ratio?

The commonly used 7:1 ratio for cat years to human years is not very scientifically accurate. This ratio suggests that for every 1 human year, a cat ages 7 years. So a 1-year-old cat would equate to a 7-year-old child. While this ratio provides a rough approximation for comparing cat and human ages, research shows that cats actually age much faster than this in their first 2 years, and slower than this ratio after.

According to studies, cats reach the human equivalent of 15 years in just the first year of life. In the second year, they are around 24 human years old. After this, the aging slows down. Experts estimate a 2-year-old cat is similar to a 28-year-old human. After year two, cats age around 4 human years for every cat year. So a 6-year-old cat would be around 41 human years old using the more accurate formula.

The takeaway is that the commonly used 7:1 ratio overestimates the first 2 years and underestimates later years. More accurate formulas account for the rapid kitten development phase and the slowing as cats become seniors. While the ratios provide approximation, the most reliable way to assess a cat’s age is through regular veterinary exams to gauge health and development.

Alternatives to cat years

While the traditional 7:1 ratio for cat years is well known, it is an oversimplification. Cat aging is not linear, and factors like breed, lifestyle, and genetics impact lifespan. Some experts have proposed alternative formulas to more accurately reflect cat aging compared to humans.

One popular alternative formula was created by Dr. Fred Metzger, DVM. His formula takes into account that cats mature faster than humans in early life but slow down as they age. The formula is:
– 1st year = 15 human years

– 2nd year = 9 human years
– 3rd year = 4 human years
– 4th year and beyond = 4 human years per cat year

So according to Dr. Metzger’s formula, an 8 year old cat would equate to 52 human years (15 + 9 + 4 + 24). Other experts like Tracie Hotchner, author of The Cat Bible, also propose revised ratios to better capture the rapid development and aging patterns in cats.

While these alternative formulas aim to be more accurate, some argue that the entire notion of cat years is flawed. Cats do not experience aging the same as humans, so applying human years may not properly represent their experience. In the end, a cat’s actual chronological age may be more meaningful than attempting conversion to human years.

Usage and meaning today

Nowadays, the concept of “cat years” is commonly used to help pet owners understand their cat’s relative age and life stage compared to a human. While not scientifically precise, referring to a cat’s age in “cat years” can provide a rough approximation for gauging a feline’s maturity level.

For example, a 1-year-old cat would be around 15 in “cat years,” indicating it is young and energetic like a teenage human. Meanwhile, a 10-year-old cat would equate to about 70 in “cat years,” suggesting it is entering senior status. Though an imprecise comparison, this framework helps give cat owners perspective on their pet’s age.

According to veterinarians, the 7:1 ratio for calculating cat years is an oversimplification, as cats age rapidly in the first 2 years but then plateau in maturity. Still, using “cat years” serves as a shorthand for conveying a cat’s approximate human-equivalent age. This can be useful in conversations, making sense of developmental stages, and monitoring age-related health issues. While not scientifically sound, the notion of “cat years” persists as a way for cat lovers to contextualize their pet’s longevity.[1]


The concept of cat years originated in the early 20th century as a way to help people understand the shorter lifespan of felines compared to humans. Though the exact origins are unclear, references to cat years began appearing in popular media in the 1920s and 1930s. The 7:1 ratio, equating 7 human years to 1 cat year, became a popular shorthand despite lacking scientific accuracy. While some vets and researchers have proposed alternative formulas, the 7:1 ratio persists in pop culture and everyday usage. Though not literally true, cat years help symbolize the briefer lives of our feline friends and remind us to cherish our time with them. While the science is imprecise, cat years capture our intuitive sense that cats age more rapidly than humans. So this shorthand has endured as a way to approximate feline aging and appreciate the full life of a cat. Though the details remain fuzzy, cat years will likely persist as a way to articulate the unique lifespan of our furry companions.

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