Free tool, real vet math
Dog Age Calculator
This free dog age calculator shows your dog’s age in human years using the size-adjusted math veterinarians actually reference, not the “multiply by 7” myth. The UCSD DNA-clock formula is thrown in for the science nerds. Add a photo and get a card worth sharing.
Dog years to human years chart
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 3 years | 28 | 29 | 30 | 31 |
| 4 years | 32 | 34 | 35 | 38 |
| 5 years | 36 | 39 | 41 | 45 |
| 6 years | 40 | 44 | 46 | 52 |
| 7 years | 44 | 49 | 52 | 59 |
| 8 years | 48 | 54 | 57 | 66 |
| 9 years | 52 | 59 | 63 | 73 |
| 10 years | 56 | 64 | 68 | 80 |
| 12 years | 64 | 74 | 79 | 94 |
| 14 years | 72 | 84 | 90 | 108 |
| 16 years | 80 | 94 | 101 | 122 |
Human-year equivalents. Small: under 20 lb. Medium: 21 to 50 lb. Large: 51 to 90 lb. Giant: over 90 lb.
How the math works
The first year of a dog’s life is worth roughly 15 human years, and the second adds about 9 more, because dogs sprint through puppyhood and adolescence. From age two onward, aging slows to a per-year rate that depends on adult size: about 4 human years per dog year for small breeds, 5 for medium, 5.5 for large, and 7 for giant breeds. That is why a 10-year-old Chihuahua and a 10-year-old Great Dane are in very different chapters of life.
The bonus number comes from a 2020 UC San Diego study that matched DNA methylation patterns between Labradors and humans, producing the formula: human age = 16 × ln(dog age) + 31. It says a 1-year-old dog is molecularly similar to a 31-year-old human, which surprises everyone at parties. We show both numbers because honesty about the math is kind of our thing.
Dog age questions, answered
Is the "multiply by 7" rule true?
No. It has never appeared in any veterinary guideline. Dogs mature very fast in their first two years (a one-year-old dog is roughly a 15-year-old human), then aging slows to a size-dependent rate of about 4 to 7 human years per dog year. That is the math this calculator uses.
Why does my dog’s size matter?
Small dogs age slower in adulthood and routinely live into their late teens, while giant breeds age fastest and have shorter lifespans. Veterinary age charts therefore use different per-year rates for small, medium, large, and giant dogs after age two.
What is the epigenetic clock number?
A 2020 study from UC San Diego compared DNA methylation patterns in dogs and humans and derived the formula: human age equals 16 times the natural log of the dog’s age, plus 31. It runs hot for young adult dogs and is shown here as a bonus reference for dogs over one year old.
When is a dog considered a senior?
As a rule of thumb: around 11 years for small breeds, 10 for medium, 8 for large, and 7 for giant breeds. Gray muzzles are earned, and senior dogs make some of the most beautiful portraits we print.
Is this calculator really free?
Completely. No account, no email, and the photo you add to the card never leaves your device. We make custom pet portraits for a living and this is our gift to dog people.
Put this calculator on your site
Bloggers, groomers, vets, rescues: embed it free. Copy, paste, done.
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<script>window.addEventListener("message",function(e){if(e.origin==="https://www.petpicportraits.com"&&e.data&&e.data.pppEmbed==="dog-age-calculator"){var f=document.getElementById("ppp-dog-age-calculator");if(f)f.style.height=e.data.height+"px"}});</script>
<p style="font-size:14px"><a href="https://www.petpicportraits.com/dog-age-calculator">Dog age calculator</a> by <a href="https://www.petpicportraits.com">Pet Pic Portraits</a></p>That photo deserves more than a card
Turn it into a custom portrait: free preview in about 30 seconds, hand-reviewed by a real person, and nothing prints without your approval.
See your dog as art (free preview)Cat person too? Try the cat age calculator. Or see all free pet calculators.