Life expectancy calculators are based on age, gender, year born, height, weight, dietary habits, lifestyle, family medical history and geographical location. Calculations are created on using this information as an average made up of large amounts of population data.
How long a person may live, statistically, is based on health and genetic data as well as geographical locations.
Calculations are determined using the year of birth, current age and demographic factors including gender. Calculations take into account that at a given age, the average number of years that would be lived by a certain group of people. It is measured that these same people live in the same area and are exposed to same lifestyles and environment.
Studies done by the Social Security Administration show that a man reaching the age of 65 can expect to live until age 84.3 and a woman turning 65 can expect to live until 86 on average, without taking into account the other important factors such as general health and lifestyle.
Mathematically, life expectancy is the number of years of life remaining at a given age, which means the average number of subsequent years of life for someone now aged "x." Because life expectancy is an average, people may die many years before or many years after their expected survival date.