Convert your cat's age to human years. The first 2 years age rapidly — the old 7x rule does not apply to cats.
A 1-year-old cat is roughly equivalent to a 15-year-old human. At 2 years, about 24 human years. After that, each cat year equals roughly 4 human years. Indoor cats typically live 12–18 years; outdoor cats average 5–7 years due to hazards.