Dog Age Calculator
Convert your dog's age to human years using the modern veterinary formula by breed size — small, medium, or large.
More accurate than the old 7:1 rule.
Dog age in human years is far more nuanced than the old “multiply by 7” rule. Modern veterinary science uses a DNA methylation model developed by researchers at UC San Diego, which better reflects how dogs actually age biologically.
The scientific formula (small/medium breeds):
Human Age = 16 × ln(Dog Age) + 31
Where ln is the natural logarithm.
Simplified reference table:
| Dog Age | Human Equivalent |
|---|---|
| 1 year | ~31 years |
| 2 years | ~42 years |
| 4 years | ~52 years |
| 7 years | ~62 years |
| 10 years | ~69 years |
| 15 years | ~83 years |
This model explains why a 1-year-old dog is sexually mature (equivalent to a young adult), while aging slows significantly in middle and later years — just like humans.
Size correction: Large and giant breeds age faster than small breeds:
- Small breeds (under 20 lbs): Use the formula as-is
- Medium breeds (20–50 lbs): Add 1–2 human years after age 6
- Large breeds (50–90 lbs): Add 3–5 human years after age 5
- Giant breeds (90+ lbs): Add 5–8 human years after age 4 — Great Danes average only 8–10 years of life
Worked example: A 6-year-old Labrador Retriever (large breed): Base: 16 × ln(6) + 31 = 16 × 1.792 + 31 = 59.7 → ~60 human years Size adjustment: +4 years → ~64 human years
Why this matters: Knowing your dog’s true biological age helps you schedule appropriate vet screenings, adjust diet and exercise, and recognize age-related health changes at the right time.