How to work out your dog’s age in human years
- Enter your dog’s age in years, and months if you know them.
- Read the human age from the epigenetic formula, with the 7-year rule beside it for comparison.
- Use the chart below the result to see how the two methods compare from 1 to 16 years.
Why the 7-year rule is wrong
The 7-year rule assumes dogs age at the same steady rate all their lives. They don’t. A dog reaches adulthood within its first year or two and then ages more slowly. The rule also treats a Chihuahua and a Great Dane the same, though large breeds usually live shorter lives. It probably comes from comparing a typical human lifespan with a typical dog’s, which gives a rough average but not a good year-by-year match.
The epigenetic formula
The formula is human age = 16 ln(dog age) + 31. Because it’s a logarithm, the human age climbs steeply at first and then levels off:
| Dog age | Human age (formula) | 7-year rule |
|---|---|---|
| 1 year | 31 | 7 |
| 2 years | 42 | 14 |
| 3 years | 49 | 21 |
| 4 years | 53 | 28 |
| 6 years | 60 | 42 |
| 8 years | 64 | 56 |
| 10 years | 68 | 70 |
| 12 years | 71 | 84 |
| 14 years | 73 | 98 |
| 16 years | 75 | 112 |
The two methods agree only around 10 years. Before that the 7-year rule makes dogs seem too young, and after it too old. For cats, the cat age calculator uses the rule vets commonly give.