Blog · 6 November 2026
How old is my dog in human years?
The short answer: a 1-year-old dog is about 15 in human years, a 2-year-old is about 24 — and from there it depends on your dog's size. A 10-year-old small dog is about 56 in human years; a large dog the same age is about 66. The old “multiply by 7” rule gets all of that wrong, and this page shows you the two published methods that replace it: the American Kennel Club's size-based chart and the UCSD DNA-age formula.
The AKC chart: dog years to human years by size
The chart below is the American Kennel Club's published table, based on guidance from the American Veterinary Medical Association. Every size is identical through age 5 — a 5-year-old dog is 36 in human years whatever its size — and the sizes diverge from age 6, because larger dogs age faster in later life.
| Dog's age | Small (up to 20 lb) | Medium (21–50 lb) | Large (51–100 lb) |
|---|---|---|---|
| 1 year | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 |
| 3 years | 28 | 28 | 28 |
| 5 years | 36 | 36 | 36 |
| 7 years | 44 | 47 | 50 |
| 10 years | 56 | 60 | 66 |
| 12 years | 64 | 69 | 77 |
| 15 years | 76 | 83 | 93 |
Source: American Kennel Club, “How to Calculate Dog Years to Human Years” (akc.org). The AKC publishes whole-year values for ages 1–16; the figures above are those published values. Between whole years our dog age calculator interpolates in a straight line between chart years.
Why “multiply by 7” is wrong
The ×7 rule makes a 1-year-old dog a 7-year-old child, when it is actually close to a mid-teenager on the chart — and it makes a 15-year-old dog 105, far beyond any sensible equivalent. Dogs do most of their growing up in the first two years and then age more gradually, which no single multiplier can capture. The first year alone is worth about 15 human years, the second adds about 9 more, and only after that does the yearly step settle down — roughly 4 a year for small dogs, 5 for medium and 6 for large.
The UCSD formula: the DNA-age view
In 2020, Wang and colleagues at UC San Diego published a study in Cell Systems comparing DNA methylation — an epigenetic ageing clock — in 104 Labrador Retrievers and humans. Fitting the two curves gave a formula: human years = 16 × ln(dog age) + 31. On it, a 2-year-old dog is about 42, a 5-year-old about 57 and a 10-year-old about 68 in human years. It runs higher than the AKC chart in early and middle life, because it measures biological ageing at the DNA level rather than the life-stage convention vets use.
One honest limitation: the study used Labradors only, so the formula says nothing about size. That is why our calculator shows both numbers side by side — the size-based chart and the science formula — and labels which is which. Neither is a medical measurement; both are population-level comparisons.
Which number should you actually use?
For day-to-day care decisions — when to switch to senior food, how often to book vet checks, how much exercise is sensible — use the AKC size chart and the life stage that goes with it. Large dogs reach the senior stage years before small dogs: roughly from age 7 for large dogs, 8 for medium and 10 for small. Use the UCSD formula when you want the biological-age view, for example to understand why a 2-year-old dog already behaves like a young adult rather than a toddler. If the two numbers disagree, that is the point: they measure different things, and neither replaces a vet's judgement of your individual dog.
Age is only half the question. Life stage also drives feeding: a senior dog needs fewer calories than the adult it was at five. Work out the daily figure with the pet feeding calculator, which uses the veterinary RER × MER method, or check the cat age calculator if you share your home with a cat too — cats follow a different chart (15, then +9, then +4 a year).
Quick answers
How old is a 5-year-old dog in human years?
36 on the AKC chart, for every size — small, medium and large are all identical through age 5. On the UCSD formula the same dog is about 57.
How old is a 10-year-old dog in human years?
About 56 for a small dog, 60 for a medium dog and 66 for a large dog on the AKC chart — size matters a lot by this age. The UCSD formula gives about 68 for all sizes.
Is my dog a senior yet?
Roughly from 10 years for small dogs, 8 for medium and 7 for large. The dog age calculator labels the life stage from size and age together.
Sources
- American Kennel Club — How to Calculate Dog Years to Human Years (size-based chart, based on AVMA guidance).
- Wang et al., UC San Diego — Quantitative Translation of Dog-to-Human Aging, Cell Systems (2020) — human years = 16 × ln(dog age) + 31, from 104 Labrador Retrievers.
- 2019 AAHA Canine Life Stage Guidelines — senior-stage timing by size. See our About & Sources page for the full list.
Disclaimer: General guidance only, not veterinary advice. Age conversions are comparisons to help you plan care, not medical measurements. If your dog is unwell, losing or gaining weight unexpectedly, or ageing faster than expected, see a vet.