How do “cat years” convert to human years?

At cat years, we love our cats more than anything and just want better years with our cats. Cats age much faster than people, especially in the first two years of life. A common conversion: year one ≈ 15 human years, year two ≈ 24, and every year after adds about 4 “cat years”. By that math, a 10-year-old cat is roughly 56 in human years.