Dog Years to Human Years Chart

Full chart: dog years to human years, by size

Every value below comes from the same formula the dog age calculator uses: year 1 equals 15 human years for any size, year 2 adds 9 more (24 total), both AVMA's own published figures, and from year 3 onward each additional dog year adds a size-dependent 4 (small), 5 (medium), 6 (large) or 7 (giant) human years, a widely used simplification of the size-based pattern (see the sourcing section below).

Note that few giant-breed dogs live to 18-20 years in practice; those rows are included for completeness of the formula, not as a typical outcome. See the dog life stages page for how these ages map onto puppy, adolescent, adult and senior stages.

Why the chart isn't a straight multiplication

Notice that the same dog year is worth different amounts of human years depending on when it happens: year 1 alone is worth 15 human years, but the 10th dog year (going from 9 to 10) is only worth between 4 and 7 human years, depending on size. That's the entire reason the "multiply by 7" rule fails so badly: it assumes every dog year is worth the same amount, when in reality the very first year or two of a dog's life covers a huge amount of biological development (going from a newborn to a physically and sexually mature young adult), while later years are comparatively more like ordinary adult aging.

Where these numbers come from

Years 1 and 2 come directly from guidance published by the American Veterinary Medical Association (AVMA), quoted by the American Kennel Club: "15 human years equals the first year of a medium-sized dog's life. Year two for a dog equals about nine years for a human." That part of the chart is identical across all four size categories and isn't in dispute between sources.

The size-dependent rate from year 3 onward (4/5/6/7 per additional dog year) is a different kind of number: it's a widely used simplification, also used by sites like Chewy and Pumpkin Pet Insurance, of a more detailed pattern documented by veterinary references such as the American Animal Hospital Association's (AAHA) published canine age chart (sourced to the Dog Owner's Home Veterinary Handbook, 4th edition). AAHA's real chart isn't a flat rate at all, it gives an exact number for every single year and size, and that number moves unevenly (its large-breed column, for example, averages closer to 5.3 human years per dog year than a flat 6, and its small-breed column happens to match a flat 4 exactly). This site uses the simplified flat version because it's the version most people are already familiar with, and because a flat per-year rate can be interpolated smoothly to a partial (years-and-months) age, something a table of whole-year values alone can't do without the same kind of interpolation this site already discloses below. Either way, this is a genuinely different (and better-supported) claim than the old x7 rule, which has no real veterinary research behind it at all, it's simply a rough average that happens to divide a typical human lifespan by a typical dog lifespan.

The 2019 natural-log formula: a different, narrower method

A separate, frequently cited alternative comes from a 2019 epigenetic-clock study: it proposes converting a dog's age using the formula human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. It's a genuinely interesting piece of research, but it comes with an important caveat that's often left out when it's quoted: the study's underlying data was drawn from Labrador Retrievers, a single medium-to-large breed, so its accuracy for a Chihuahua or a Great Dane is unproven. This calculator uses AVMA's own year 1-2 guidance plus a size-adjusted rate instead specifically because it already accounts for size differences directly, rather than applying one breed's aging curve to every dog.

How partial years (months) are handled

The whole-year milestones in the table above are this site's own simplified (flat-rate) figures, built as described in the sourcing section above: AVMA's own numbers for years 1-2, then a flat industry-standard rate for year 3 onward. For a dog that's, say, 4 years and 6 months old, this site's dog age calculator interpolates in a straight line between the 4-year and 5-year milestones for that dog's size, rather than rounding to the nearest whole year. That's a reasonable, disclosed estimate for a value between two known points, not a separately published figure, and it's precise enough for the practical purpose most people want an age chart for: getting a general sense of a dog's stage of life.

Using the chart alongside the calculator

The chart above is useful for quickly comparing a few ages at a glance, or for checking a calculator result against the published milestones directly. For an exact figure for your own dog, including months, use the dog age calculator on the homepage, pick the closest size category, and the tool does the interpolation for you instantly. If you want to know what actually changes at each stage of your dog's life, rather than just the number, see the dog life stages page next.

Your entries stay private

This page displays a static reference chart, no input is collected here at all. If you use the calculator on the homepage, every calculation runs locally in your browser and nothing is sent to a server; see the privacy policy for the full detail.