What this calculator does
This tool estimates how old your dog would be in equivalent human years. Rather than the old rule of thumb of simply multiplying by seven, it uses a size-adjusted approach reflecting that dogs mature quickly in their first two years and that larger breeds tend to age faster in later years than smaller breeds.
How the math works
The first year of a dog’s life is treated as roughly 15 human years, and the second year adds about 9 more human years, reflecting rapid early development. After age two, each additional dog year adds a fixed number of human years that depends on adult size: about 4 years per dog year for small breeds, up to about 7 years per dog year for giant breeds, since larger dogs generally have shorter lifespans and age faster later in life.
Good to know
This is a widely used approximation for general educational and planning purposes, not an exact biological or veterinary measurement — individual dogs vary by breed, genetics, and health. For specific health or aging concerns about your pet, consult a veterinarian.