How the SSA life table works.

The first column is a death probability: the chance that a person at that exact age dies within the next year, under the mortality rates for the period. It is written as a decimal, so 0.003115 at age 40 means about three deaths per thousand men at that age in that year.

The second column is the number of survivors. It starts at 100,000 at age 0 and shrinks as the death probabilities are applied year by year. It is not a real group of people. It is a fixed reference population that makes rates comparable across the whole table, the same way a batting average makes two seasons comparable.

The third column is life expectancy: the average number of years remaining at that exact age. It is the column this site publishes. It is produced by adding up the survival time of the reference population from that age onward and dividing by the number still alive.

Because the three columns come from one chain, they must agree. A higher death probability reduces the survivors column faster and shortens the remaining-years column. That is why the remaining-years column falls smoothly with age instead of jumping around: it is a summary of the same underlying schedule.

The SSA calls this a period life table. It is based on the mortality experience of a population during one relatively short period, here the single year 2023. Those rates are then applied to a hypothetical group for the rest of its life.

That construction has a consequence worth stating plainly. A period table holds mortality constant at one period's level. It does not assume that medicine, safety, air quality or living standards will keep improving. Real cohorts usually do experience some improvement, so a period table is not a prediction of how long today's 40-year-olds will actually live.

The alternative is a cohort table, which follows one group born in the same year and includes projected future improvements. The SSA publishes period tables in this series. We use the period table because it is the one named in the release and it is the one whose numbers can be checked against the published page.

The release also defines its population. The Social Security area population includes residents of the 50 states and the District of Columbia, civilian residents of Puerto Rico, the Virgin Islands, Guam, American Samoa and the Northern Mariana Islands, federal civilian employees and service members abroad with their dependents, non-citizens abroad who are insured for Social Security benefits, and other U.S. citizens abroad. It is not simply the population of the 50 states, which is why we describe it with the agency's own term.

The SSA defines its life-expectancy column for a person at an exact age, born on January 1, using the mortality rates for the period across their remaining life. Two details follow from that wording.

First, the row is for an exact age, not an age band. There is no 35-to-44 group in this table. Each age from 0 upward has its own row, which is why the published file is long and why our transcribed file keeps one row per age.

Second, the stated convention is a birthday of January 1. Real birthdays fall on every date, so the remaining-years value is an average over the year rather than a value computed for your own birthday. The methodology page explains how this site handles the gap between birthdays.

One more limit is worth naming. A period table gives a mean, not a median. It does not tell you the age by which half of a group has died. Turning a mean into a personal survival probability would need more information than the table carries, so we do not do it.

Our U.S. calculator data file contains the life-expectancy value for each sex, for exact ages 18 to 110. That is the value the death clock calculator reads and the value listed on the life expectancy by age page.

This article also reproduces death-probability and survivor values for six selected ages to explain the table. Neither column is used by our calculator. For the full set of published columns and ages, use the free SSA source linked below.

Our U.S. calculator data file covers ages 18 to 110, a subset of the SSA source table. The article's age-0 example does not extend calculator coverage. Our UK transcription covers ages 18 to 100. No estimate is offered outside the selected file's age range, and missing values are not extrapolated.

To see the male and female columns compared across ages, read life expectancy by sex. To compare the United States with the United Kingdom, read life expectancy by country.