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.

dog and owner

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:

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.

dog and owner

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.

A senior beagle and man look at each other.

Dr. Sarah Wooten Dr. Sarah Wooten

Dr. Sarah Wooten graduated from UC Davis School of Veterinary Medicine in 2002. A member of the American Society of Veterinary Journalists, Dr. Wooten divides her professional time between small animal practice in Greeley, Colorado, public speaking on associate issues, leadership, and client communication, and writing. She enjoys camping with her family, skiing, SCUBA, and participating in triathlons.

Related articles

What to Feed Your Pregnant or Nursing Dog

Proper nutrition for your pregnant or nursing dog is vital to her and her puppy's health. Learn what you should do provide her with the proper nutrients.

How to Choose a Dog Life Jacket

If your dog is often in or around water, a dog life jacket can help keep them safe. Learn which dogs might need one & key features to help you choose.

How to Leash Train a Puppy

Get helpful tips and advice on how to properly leash train your new puppy to help make your walks together safer and more enjoyable.

Acupuncture for Dogs: How It Can Help, What to Expect & More

Learn the basics of acupuncture for dogs, including the conditions it can treat, what to expect during a session and potential side effects.

Why Do Female Dogs Hump Things?

Why do female dogs hump things? Learn the reasons behind this curious behavior and ways you can help curb her mounting habits.

Dog Jumping: Why They Jump & How to Train Them Not To

Learn common reasons why dogs like to jump on you, interesting facts about breeds that jump the most & highest, and how to stop their jumping behavior.

Dealing With a Dog Peeing on the Lawn

Discover why dead spots in your green lawn could be caused by dog urine, and learn steps you can take for getting your lawn (& dog) back into shape.

Fostering a Puppy: A How-To Guide

First-time foster parents: Learn about the process of fostering a puppy or dog, including how to prepare, challenges & rewards that come with it.

Why Do Dogs Paws Smell Like Corn Chips?

You're not the only pet parent out there wondering, "Does My Dog Smell Like Corn Chips?" Learn why this is such a common smell your pup might give off.

Tips for Traveling with Your Dog in the Car

Taking your pup on a road trip? Learn the safest means of traveling with dogs in a car.

Recognizing and Managing Dog Dementia

Learn the common signs of dog dementia & canine cognitive dysfunction, how it is diagnosed and possible treatments that can be taken to manage the disease.

My Dog Ate Raw Chicken: What Should I Do?

My Dog Ate Raw Chicken: What Should I Do?

The Facts Behind Breed-Specific Dog Food

Choosing the right food for your puppy is a challenging task, and a very important one. Learn ,more about breed specific dog foods.

Heart Disease and Conditions in Dogs: Causes & Facts

Learn what heart disease and heart conditions are for dogs, their causes, how to spot the symptoms, and what to do if you suspect it in your dog.

Keys to Helping Your Dog Through the Aging Process

Understand the different ailments that can affect aging dogs and what you can do to provide them with the quality of life they're used to living.

Why Dogs Roll in Poop (and Other Smelly Things)

Learn why dogs roll in poop and other stinky things, what you can do to stop this behavior, and how to clean them up when they do.

Building a Dog Park in Your Own Backyard

Learn how to create your own backyard dog park, possibly with materials you already have, so that your dog can enjoy the benefits of a dog park at home.

Helpful Tips for a Teething Puppy

Teething is a part of a puppy's life. Use these 3 tips to help your puppy through this difficult time and protect your household from teething incidents.

Getting Rid of Your Dog's Ear Mites

Ear mites in dogs can cause your pup irritation & pain. If you think his ear scratching might mean he has mites, learn what to do for treatment.

Common Health Concerns to Look for in Puppies

Watch out for these 6 common health issues that puppies may develop in their first year of life. Learn all the symptoms so you can provide the best care.