A death clock is a life expectancy calculator. Some of the factors considered in the calculation are age, gender, geographic location, amount of tobacco and alcohol consumed, emotional outlook, and body mass index.
There are dozens of websites that contain versions of the death clock algorithm. All of them begin with the user's average life expectancy, subtract the user's current age and add or subtract modifiers for other variables. Not all death clocks contain the same list of variables; for example, some require the user to enter the amount of alcohol or tobacco consumed and others simply ask whether or not the user smokes or drinks alcohol.