Data method
Period vs Cohort Life Expectancy
Period and cohort life expectancy answer related but different questions. Knowing the difference keeps the number from sounding more certain than it is.
Period life expectancy
A period table uses mortality rates from a specific period and applies those rates across the rest of a hypothetical life. It is a snapshot of current or recent mortality conditions.
The SSA actuarial table used here is a period table, which makes it straightforward for public lookup by age and sex.
Cohort life expectancy
A cohort estimate follows a real birth cohort through time, or projects how mortality may change as that cohort ages. It can reflect future improvements or setbacks, but it depends more heavily on assumptions.
Cohort estimates can be useful for forecasting. Period estimates are simpler and more transparent for a public calculator.
Why this site labels the method
A life expectancy number should always say what kind of table it came from. Without that, users may assume it is a personal forecast or a promise about the future.
This site uses the period-table result because the source is public, official, and easy to verify.