It's possible to do a basic life expectancy calculation based on a person's age and gender, but there's no real way to know how accurate that estimate is for any given person without knowing more about his or her medical history. You can figure out a more detailed estimate by combining information about a person's chronic conditions, medical conditions, blood pressure, body mass index, and hospitalization history, but it turns out you can get just as good an answer with ten feet of pavement and a stopwatch. Your walking speed can tell a lot about you—including your life expectancy.