Dog age calculator
The “multiply by seven” rule is a myth. Dogs age fast early and then slow down, and the rate depends on breed size. This calculator converts your dog’s age into human-equivalent years using a size-aware formula, so owners get a realistic picture of their pet’s life stage.
How it works
Aging is split into three phases:
- First year ≈ 15 human years
- Second year ≈ 9 more human years (so a 2-year-old ≈ 24)
- Each year after counts for a size-dependent rate
| Size group | Weight | Per-year rate after age 2 |
|---|---|---|
| Small | up to 9 kg / 20 lb | 4 |
| Medium | 9–23 kg / 20–50 lb | 5 |
| Large | 23–41 kg / 50–90 lb | 6 |
| Giant | over 41 kg / 90 lb | 7.5 |
Small breeds mature fast but live longer, while giant breeds age faster after maturity — which is why a single multiplier is too crude.
Example
A 3-year-old medium dog:
15 (year 1) + 9 (year 2) + 5 × (3 − 2) = 29 human years
A 5-year-old giant breed: 24 + 7.5 × 3 = 46.5 human years. Enter the age, pick the size group, and get the human-equivalent age instantly — all in your browser.