How to Compare Dog Years to Human Years

You adore your dog, so naturally you want them to live as long as possible. For many pet parents, this line of thinking often leads to researching how to compare dog years to human years. Understanding a dog's age in human years can help put things into perspective — but is there a reliable way to do it? An old saying asserts one dog year equals seven human years. However, modern research shows converting dog years to people years is more complex.

Read on for a deep dive into dog lifespans, including the life expectancy of large dogs versus small dogs, ways to compare dog years and people years, and tips to help your dog live the longest, best life possible.

A Dog's Lifespan: What to Expect

Many factors can affect a dog's lifespan, from size to nutrition. Here are some of the key influential factors.

Breed Size

Comparing large dog years to human years is different than comparing small dog years to human years. This is because, in general, small dogs live longer than large dogs.

Large dogs may age faster due to the strain their size puts on their bodies. For example, larger dogs are at higher risk of arthritis due to more wear and tear on their joints. Another theory suggests large dogs are more susceptible to cancer than small dogs due to their rapid growth.

When Dogs Become Seniors by Size

While science is still trying to uncover the exact reasons, the American Veterinary Medical Association provides some rough estimates for when different-sized dogs become seniors, meaning they've reached the last 25% of their breed's estimated lifespan:

• Small or toy breeds (less than 20 pounds): 8 to 11 years

• Medium-sized breeds (20 to 50 pounds): 8 to 10 years

• Large breeds (50 to 90 pounds): 8 to 9 years

• Giant breeds (more than 90 pounds): 6 to 7 years

Other Factors

When considering your dog's lifespan based on their size, remember "averages" are general observations, and other factors are at play. For example, Labrador retrievers (a large breed) can live over 13 years with the right care and supporting circumstances.

Here are some other factors that can affect a dog's lifespan:

• Genetics

• Face shape (brachycephalic breeds are prone to respiratory issues)

• Chronic disease or parasites

• Weight (lean dogs tend to live longer than overweight dogs)

• Nutrition

• Veterinary care

How to Compare Canine Years to Human Years

You may have heard of the "7:1 ratio" used to compare people years to dog years. This ratio is based on the assumption that the average dog lives to 10 and the average human lives to 70. However, we now know this ratio isn't reliable, especially when you consider how many factors affect lifespan. So, how do you calculate a dog's age, and can you compare dog years to human years?

A study comparing dog and human genomes showed that, in terms of genetics, comparing dog years to people years is like comparing apples to oranges. Specifically, a young dog's genome changes much more rapidly than a young human's. The researchers found the comparison of dog years to human years is nonlinear at best, debunking the 7:1 ratio.

Converting People Years to Dog Years

As tempting as it is, you can't accurately calculate a dog's lifespan in human years. If you want to try it anyway, the American Kennel Club provides these guidelines to estimate a medium-sized dog's age in human years:

• Year one of a dog's life equals 15 human years.

• Year two equals about nine human years.

• Each human year equals approximately five dog years after that.

How to Help Your Dog Live Longer

While you can't control your dog's size and genetics, you can improve their chances of living a long, healthy life by prioritizing the following:

• Complete and balanced nutrition

• Regular veterinary wellness care, including parasite control, exams and vaccinations

• Dental care, including at-home and professional cleanings

• Daily exercise and mental stimulation

• Weight control

Your Dog's Best Life

The best way to think about your pup's lifespan is the age of a dog in dog years. It can be tempting to get wrapped up in a dog's age in human years, but that isn't what will help your dog live long or live well. Feeding your dog the right amount of high-quality food, taking them in for regular veterinary care, and providing daily exercise and attention go a long way toward your pup's health and happiness.