According to Dr. Jennifer Coates, a veterinarian who writes for PetMD, a cat’s life expectancy ranges from 10 to 15 years with the average being 14 years.

This, however, applies only to indoor cats. Cats that roam outside have an average life expectancy of seven years – half as long as their indoor cousins.

Some cats, of course, can live longer than that, with some felines living to be 20 years old or more.

What is the aging process like in cats?

For generations, people believed that cats aged five years for every human year. Thus, a three-year-old cat would be comparable to a 15-year-old human.

The trouble is most cats are actually finished growing by the time they’re a year old, so a three-year-old cat is physiologically much older than a human teenager.

The American Animal Hospital Association (AAHA) devised a new way of determining a cat’s age. According to their chart, cats age 24 years during their first two years of life.

They then age four years for every year after. So, a three-year-old cat would be comparable to a human of 28, while a 15-year-old cat would be comparable to a human of 76.

The AAHA also divides a cat’s life into six stages: kitten, junior, prime, mature, senior, and geriatric. A kitten is a young cat that hasn’t hit puberty yet, while a junior is a feline adolescent.

Prime and mature cats are, respectively, young and middle-aged adults. Older cats fall into the last two categories. If Tillie the Tortoiseshell is 12 years old, for example, she would be considered a senior.

What is a tortoiseshell cat?

According to Denise LeBeau, a writer for “Catster,” the word “tortoiseshell” doesn’t describe a breed but a coat pattern.

A tortoiseshell cat or “tortie” is one that has a mixture of black and orange fur, and a dilute tortoiseshell has grey and peach fur.

A tortoiseshell cat that also has white blotches is often called a calico or tricolored cat. A “torbie” is a tortoiseshell cat that also has the stripes and spots of the tabby.

Is it true that tortoiseshell cats and calicos are always girls?

Torties and calicos are nearly always female, and the reason has to do with genetics. Julianna LeMieux, a writer for the American Council on Science and Health explains the mechanism that results in the birth of a tortoiseshell or calico cat.

Cats, like humans, have two sex chromosomes, X and Y. Each cat inherits a single chromosome from each parent. Girl cats end up with two X chromosomes, while boys receive an X and a Y chromosome.

One of the genes that determine coat color is located on the X chromosome. This gene has two alleles or versions; one results in a black coat and the other gives the cat an orange coat.

Since male cats have only one X chromosome, they can only inherit a single allele that will make them black or orange.

A female cat, however, is XX and can inherit both alleles. Very early during development, one of the X chromosomes in each cell will become inactive and form a Barr body, and the other X chromosome will provide the cell with instructions on which genes will be expressed.

Those instructions determine what color a given patch of fur will be. The result will be a cat with patches of black and orange fur.

Other genes determine if the cat will also have white blotches and be a calico or have stripes and be a torbie (tortoiseshell tabby).

Dr. Mary Becker, a veterinarian, and writer, for “Vet Street” notes that tortoiseshells and calicos can be male – but it’s very rare. Only one cat in 3000 calicos or torties will be a boy.

These cats have a condition called Klinefelter Syndrome, which can also occur in humans. Males with the condition have an extra X chromosome, so they are XXY rather than the normal XY.

That extra X chromosome means their fur coloration works like that of a female cat, so they can have black and orange patches rather than being all black or all orange like their brothers.

According to Heather M., a writer for the American Society for the Prevention of Cruelty to Animals (ASPCA), male calico and tortoiseshell cats have a variety of health problems. For example, the vast majority are sterile.

They can also have behavior problems caused by developmental and cognitive issues. Cats with Klinefelter Syndrome often have more body fat than other cats, which increases their risk of developing heart disease, joint problems, or diabetes.

They can have a reduction in their bone mineral content, and that increases the chances of their breaking a bone. Cats with Klinefelter Syndrome thus often have a reduced life expectancy.

What breeds of cats can be tortoiseshell?

According to Leslie Carver, a writer for “The Nest’s” pet section, the tortoiseshell coloration can occur in both random-bred cats and pedigreed cats. Many cat breeds produce tortoiseshell cats.

Breeds with tortoiseshell cats include the following:

  • American Bobtail
  • American Curl
  • American Shorthair
  • Birman
  • British Shorthair
  • Colorpoint Shorthair
  • Cornish Rex
  • Devon Rex
  • European Shorthair
  • Exotic
  • Japanese Bobtail
  • Maine Coon
  • Manx
  • Norwegian Forest Cat
  • Oriental
  • Persian
  • Siamese
  • Turkish Van

Pointed cats such as the Siamese have the usual creamy bodies, but their points are tortoiseshell.

How long do tortoiseshell cats live?

As mentioned earlier, tortie cat life expectancy is the same average life expectancy of any cat is around 14 years. There are a variety of factors that can affect a cat’s longevity, however.

For example, cats that are kept indoors live twice as long as cats that roam outside. Outdoor cats face such perils as cars, dogs, and a variety of diseases.

Gender also affects a tortoiseshell cat’s life expectancy. While female tortoiseshells enjoy the same life expectancy as most other cats, males all have Klinefelter Syndrome, which increases the risk of their developing health problems like heart disease or diabetes.

Cats with Klinefelter Syndrome need a vigilant owner who will take them to the vet regularly and otherwise take care of any health problems.

For example, Dr. Hanie Elfenbein, a writer for PetMD, describes the care needed by a cat with diabetes. Such care includes a low-carb diet and insulin shots.

The owner will also have to watch their cat carefully to see how they react to insulin and any other medical treatments.

With good care, a cat with diabetes can enjoy the same life expectancy as a healthy cat, but untreated diabetes can be fatal.

The breed is another factor that can affect longevity. The website “International Cat Care” described a 2015 study on cat longevity that was conducted in Great Britain. The researchers examined over 4000 veterinary records taken from 87 practices and looked for patterns.

They found that pedigreed cats generally had shorter life expectancies than did mixed-breeds: 12.5 years to 14 years.

For Further Reading

A tortoiseshell belonging to a specific breed would thus likely have a shorter life expectancy than one that did not. The researchers, however, did find that some breeds had longer life expectancies than did others.

Long-lived breeds included the Birman, Burmese, Persian, and Siamese. These cats could live at least as long as the average mixed-breed.

Conversely, Abyssinians, Bengals, British Shorthairs, Maine Coons, and Ragdolls had shorter life expectancies than did other cats.

The website PetMD maintains a section devoted to cat breeds. Their description of the American Shorthair states that is has a life expectancy of 15 to 20 years, making it a very long-lived breed.

Another website, Pet Health Network, also has a section devoted to cat breeds and also describes the American Shorthair as having exceptional longevity.

Pet Health Network also describes some of the health conditions that can appear in various breeds.


The Maine Coon, for example, may owe its comparatively short life expectancy to polycystic kidney disease and a type of heart disease called hypertrophic cardiomyopathy. Like many big dogs, it is also prone to hip dysplasia.

Barring health problems, a tortoiseshell cat can thus live as long as any other cat.