Written by Muhammad Ahtisham, dog nutrition and feeding specialist. Last updated November 8, 2026.
How to use this calculator
- Enter your dog's age in years and months.
- Pick the adult size group that fits your dog.
- Press calculate to see both estimates and the life stage.
How the dog age calculator works
I show two methods so you can see the spread. The first is the 2020 epigenetic formula from a University of California San Diego study of Labrador Retrievers: human age is about 16 times the natural log of dog age, plus 31. The second is a common size-based rule: 15 years for the first year, 9 more for the second, then 4, 5, 6, or 7 a year for small, medium, large, and giant dogs.
| Dog age | Formula | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 3 | 49 | 28 | 29 | 30 | 31 |
| 5 | 57 | 36 | 39 | 42 | 45 |
| 7 | 62 | 44 | 49 | 54 | 59 |
| 10 | 68 | 56 | 64 | 72 | 80 |
| 12 | 71 | 64 | 74 | 84 | 94 |
Life stage by size
Giant dogs are often treated as seniors from about 6 years, large dogs from 7, medium dogs from 8, and small dogs from 10. Those are rough marks, so ask your vet about your own dog.
Worked example
- A 10-year-old medium dog.
- Formula: 16 x ln(10) + 31 = about 68 human years.
- Size rule: 24 + 5 x 8 = 64 human years.
- The calculator shows both as a range, 64 to 68, and marks the dog as a senior.
What this calculator can't tell you
Dogs age at different speeds, and neither method is exact. The formula comes from one breed, and the size rule is a rule of thumb. For a broader look, read the dog years guide.
When to talk to your vet first
Dogs with kidney disease, diabetes, pancreatitis, allergies, or any other health problem need a plan from a vet. Read the terms before you change your dog's routine.