YYouLiveLong
YouLiveLong guide

How life expectancy is calculated

A plain-English guide to mortality rates, survivors, survival curves, and the area under the curve.

From one-year risks to a lifetime curve

  1. Begin with 100,000 hypothetical births. This is the life table’s radix.
  2. Apply each age’s death probability. Survivors become the starting group for the next age.
  3. Condition on current age. Divide later survivor counts by the survivor count at your age.
  4. Add the future person-years. The area below the conditional survival curve is remaining life expectancy.

This same curve supplies every milestone probability. We do not separately guess the odds of 80, 90, or 100.