Research and methodology
How LIFE Expectancy is estimated
The calculator starts with the U.S. Social Security Administration period life table for your exact age and sex, then adjusts annual mortality probabilities using only published factor estimates.
Version 2.0 · October 2026 · Statistical estimate for education only. Not a medical prediction or diagnosis.
What changes the number
Cigarette smoking
Never, former by time since quitting, or current; Li et al. plus a U.S. smoking-cessation cohort.
BMI
Calculated from height and weight; Li et al. table 2 categories.
Physical activity
Weekly moderate-to-vigorous minutes mapped to Li et al. activity categories.
Alcohol
Standard drinks converted to grams per day and mapped to sex-specific study ranges.
Sleep
Typical nightly duration using the U-shaped dose-response estimate from Yin et al.
Diet, connection, purpose, stress, broader nicotine use, and other health-context answers inform your six-pillar guidance but do not change the estimate.
Formula and safeguards
For every future age, the published annual probability is adjusted as 1 − (1 − q)^HR. The resulting survival curve is integrated to estimate remaining years.
Combined effects are capped to the joint range reported by Li et al., and the total age shift cannot exceed the study’s published 14.0-year female or 12.2-year male comparison. Individual “Add years” estimates change one factor at a time and recompute the full curve.
Primary sources
- SSA Annual Statistical Supplement 2025, table 4.C6
- Li et al., Circulation (2018)
- Thomson et al., JAMA Network Open (2022)
- Yin et al., Journal of the American Heart Association (2017)
The repository also includes the complete technical specification at docs/life-expectancy-methodology.md.