The first two years of a horses life, the horse is considered 6 and 1/2 years old. When the horse turns turns , they are age 13 in human years. When they turn three years old, they are 18 years old in human years. From then on they age roughly 2.5 human years per year. By the time the horse is 14, they are considered "aged" . By the time the horse is 36 years old, they are 100 and a half years old in human years!