Convert your dog's or cat's age into human years by size, including the epigenetic-clock estimate for dogs.
Dogs and cats grow up fast: the first year is roughly 15 human years and the second about 9 more (24 in total). After that, each year adds about 4–7 human years for dogs depending on size (larger breeds age faster) and about 4 for cats.
A 2019 study of DNA methylation in Labradors suggested another formula: human age = 16 × ln(dog age) + 31.
About 36–39 for a small or medium dog by the size chart (24 + 3 × 4 or 5), or about 57 by the epigenetic formula.
Large and giant breeds have shorter lifespans and reach their senior years sooner than small breeds.