Dog Age Calculator
Your dog's age in human years, adjusted for size.
Quick answer
- Formula: Year 1 ≈ 15 human years; year 2 ≈ +9; then +4 (small), +5 (medium) or +6 (large) per year
- Worked example — Equivalent human years (guideline): 39.0 (full example below).
Dog Age Calculator
| Equivalent human years (guideline) | 39.0 |
| Life stage | Adult |
A 5-year-old medium dog is about 39 in human years: 15 + 9 for the first two years, then 5 per year for three more — the Adult life stage.
The old 'multiply by seven' rule is too simple: dogs mature fast in their first two years and then age at a rate that depends on size. This calculator follows the commonly published AVMA-style guideline — about 15 human years for the first year, 9 more for the second, then roughly 4, 5 or 6 years per year for small, medium and large dogs.
Treat the result as a guideline, not exact science. Breed, weight, health and lifestyle all change how an individual dog ages, and your veterinarian's assessment is more precise than any table.
The formula
Worked example
A 5-year-old medium dog is about 39 in human years: 15 + 9 for the first two years, then 5 per year for three more — the Adult life stage.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Frequently asked questions
Why does size matter?
Larger dogs generally age faster and have shorter lifespans than smaller dogs, so each additional year counts for more human years in large breeds.
Is the 7-year rule ever right?
Only as a rough average for a middle-aged medium dog. It badly understates the first two years, when a dog matures from puppy to adult.
Category: Everyday Life calculators
Sources & methodology
This calculator applies the formula shown on this page exactly as written, using the standard definitions for its inputs. Results are computed from the values you enter — no data is stored — and are rounded only for display.
Content last reviewed by CalcHub Editorial.
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