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# How do Dog Years Compare to Human Years?

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• Written By: wiseGEEK Writer
• Edited By: O. Wallace
2003-2018
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Assessing dog years as compared to human years is not the simple formula many are led to believe. In general, a dog does not age seven human years for every year of life as was previously believed. A few dogs might fall into this category, but many others don’t. Instead, dog years tend to be better predicted by dog size. The largest dogs usually have the shortest life expectancies. Furthermore, altered female dogs tend to have longer lives than do altered males, or unaltered females or males. There is no complete scientific consensus on dog years versus human years, though there are a number of formulas you can evaluate.

For instance, one such formula suggests that at the end of two years of life a dog is approximately 21 years old in human years. Thereafter the dog gains four human years for each of its dog years. This formula will especially not fit dogs of a larger size, since some have a life expectancy of no more than eight or nine at most. At that rate, larger dogs would die at the human year age of about 57 years old, which to humans would be considered middle aged.

Instead you can evaluate weight of the dog, and realize that dogs that weigh more than 40 pounds are likely to be older than 21 human years by the time they are two dog years old. One formula which depends on weight suggest that a dog is 20-30 by the time they’ve reached the age of two, and that they then age four to seven years for each subsequent year of life. They may reach the geriatric stage by the time they’re nine or ten years old, and very large dogs may be considered elderly at seven or eight. Smaller dogs, especially toy varieties are likely to still be very much children when they’re two dog years old, though they have reached sexual maturity. In general, the smallest dogs have the highest life expectancies, barring poor health or obesity, and may live well into their middle teens in dog years.

As long as your dog is healthy and an appropriate weight, it can help to evaluate the dog in terms of size, sex and breed. If you have a mixed breed dog, you’ll mainly have to go by what you know about the parents in order to determine life expectancy. If the puppy is the product of several toy or small terrier breeds, life expectancy is probably in the low to mid teens. If the dog is the product of several large dogs, its life expectancy will be lower. Other factors that determine age of the dog can include nutrition, developing health conditions, and physical and emotional care of the animal. Inbreeding dogs and puppy mills tend to produce dogs that may be much more likely to age more quickly, have greater health complications, and die earlier, regardless of size.

It’s important to note that even though most dogs can have puppies by the time they are one, they still may lack in emotional maturity. Smaller dogs in particular may remain puppyish for several dog years, and good and consistent training is still needed for these animals. When a dog does start to show signs of age, such as stiffness upon waking in the morning, a little less get up and go, or the occasional bout of incontinence, do see your vet. Geriatric care for animals is ever advancing, and good veterinary care is needed to keep an aging animal comfortable and healthy.