How do you calculate a dog's age in 'dog years'?

A dog's lifespan is only a fraction of the average human's lifespan, which means that a dog ages more quickly in the same amount of time. A human of six is very young, but a dog of six is already middle aged. How can we translate a dog's chronological (actual) age into something we can compare with a human's development, maturity, and aging process? How do we know when a dog is a teenager, an adult, a senior citizen?

'Dog years' are a representation of of how old a dog would be if he lived as long as a human. On average, dogs age seven times as quickly as humans. One way to estimate how old a dog is in dog years is simply to multiply his chronological age by seven. This is probably the most popular technique for estimating a dog's physical age compared to his actual age.

Unfortunately, it's not very accurate because dogs mature much more quickly than humans do. Dogs have shorter childhoods and longer adulthoods. Dogs start walking at three weeks and reach physical maturity at 18 months. If we use the seven-for-one rule that would be the same as a human toddler walking at five months or a human child reaching physical maturity by age 11. Also, while a 15-year-old dog would be considered the equivalent of a 105-year-old person, many more dogs live to be 15 than humans live to be 105.

A more accurate formula would be: 10 and 1/2 dog years for the first two years, then four dog years per year thereafter. However, this formula does not take the dog's size into consideration. We know that small dogs tend to live longer than large dogs, as much as twice as long.

One way to handle the influence of size on a dog's aging is to change the multiplication factor used once a dog is past two years old.

for small to medium sized dogs, multiply by four
for large dogs, multiply by six
for giant breeds, multiply by eight

Using this adjustment for size we can estimate that a 65 year old human is approximately equivalent to a 12-year-old small dog, a nine-year-old old large dog or a six-year-old giant dog. It still isn't perfect, but it is more accurate than assuming dogs age the same regardless of size. We know it is rare for a large dog to make it past 12 and extremely rare for a giant dog to do so.

If all of this math is too much to face, fear not! There are several handly dog age calculators available on the Internet (see the links below). Try several and see how they compare. They may give slightly different ages in dog years depending on which formula they use for calculations.

The old rule of thumb that dogs age seven times as fast as humans comes from dividing the average human life span by the average canine life span. But it's not very accurate.

As Snopes points out, most dogs reach adulthood in roughly 18 months, which would be the equivalent of a 10-year-old child. Also, while a 15-year-old dog would be considered the equivalent of a 105-year-old person, many more dogs live to be 15 than humans live to be 105.

The handy Online Conversion site suggests that a more accurate formula would be: 10 and 1/2 dog years for the first two years, then four dog years per year. Maxie Beagle offers a scaled chart that distinguishes between small and large dogs (smaller breeds tend to live longer).

DogAge measures your dog's biological age in human years according to factors such as breed, weight, lifestyle, and behavior. You'll find another handy lifespan chart at (where else?) DogYears.com

See related links below for more information.

The old rule-of-thumb that one dog year equals seven years of a human life is not accurate. The ratio is higher with youth and decreases a bit as the dog ages. Depending on breed, a dog experiences the raging hormones of adolescence anywhere from eight months to two years or more. Generally, a dog of six years has aged about as much as a 45-year-old human. At 10, she's like a human of 65; at 12, a human of 75; and at 15, a human of 90.

For Example: for a dog that is 10 yrs. old
(the first two years) 10.5 * 2 = 21
(plus the next eight years) 4 * 8 = 32
21 + 32 = 53 years old

A dog's lifespan is only a fraction of the average human's lifespan, which means that a dog ages more quickly in the same amount of time.

Other contributors have said:

• While not that scientifically accurate, a "dog year" is 7 human years.
• Dogs age 4 years for every 1 human year.
• One human year equals 7 dog years
• To convert dog years to human years, take the dog's chronological age and multiply it by seven.
• For every year in mans life a dog ages ten years.
• it depends on height and weight
• It is said for every human year, a dog ages 7 years.
• 10.5 dog years per human year for the first 2 years, then 4 dog years per human year for each year after.
• dogs essentially "age" 7 times faster than humans.
• you multiply by 7 to get dog years, so if my dog is 3, then in dog years he would be 21.
• you might like to look further into this answer to your question about 7 yrs to every one year---By the time your dog is one you can expect him/her to be approx. 15 and 24yrs old by 2.
• first year is roughly 16, second is 24, and you keep adding 4 doggy years to one human year as the dog gets older.
• For every one dog year, there is 1/7 of a human year.
• If your dog is 6 years old in human she/he is either 30 or 32 different dogs age differently Its either 6*5 or 6*7 depending on the type the breed, and what you believe.
• you times how much years they have been with you with 8
• But now the "dog years" theory is, for the most part, discredited, because a lot of dogs live to be 13, but not a whole lot of people are 98.
• Like nearly every animal, dogs mature at a different speed. Most dogs die at, say, 10-15 years old (of old age). If you have a 13 year old dog that died of old age, it's not the same as a 13 year old human passing of old age. In dogs, a young adolescent (usually about 15 years in human years) is about 1 year old. A 1 year old human isn't even a preteen! There for, because of these reason, people needed an easier way to calculate dogs' ages. There came dog years!
• It's been a misconception for decades that every year of a dog's life is the equivalent of 7 years compared to a human's life. The actual rate at which dogs age varies, depending on the breed and size of the dog.
• I believe it's because humans have more treatment. By this I mean that humans take care of themselves by going to the doctor more, getting flu shots, wash everyday, and not only that, humans KNOW alot about their own bodies than dogs do. When a dog has a flea, all they really do is itch, but when humans have lice or something, they wash their hair or go to the doctor.

Contrary to the last statement above, many dogs do get medical care, vaccinations, baths, etc., so that really plays no role in the average years of a dog's life compared to human years.

According to Dog Owner's Home Veterinary Handbook, written by James M. Griffin MD, and Liisa D. Carlson, DVM, the actual dog's age in relation to human years is:

1 = 15
2 = 24
3 = 28
4 = 32
5 = 36
6 = 40
7 = 44
8 = 48
9 = 52
10 = 56
11 = 60
12 = 64
13 = 68
14 = 72
15 = 76
16 = 80