Why "multiply by 7" is wrong
The old rule of thumb treats aging as a flat, constant rate — but dogs actually mature very quickly in their first two years, then age at a pace that depends heavily on their size. A 1-year-old dog is already roughly equivalent to a 15-year-old human, not 7. And a giant breed ages faster in later years than a small breed does, which is part of why larger dogs generally have shorter lifespans.