How We Calculate Life Expectancy

How to calculate life expectancy: the short answer

1. Find your baseline. In a period life table, read the row for your exact age and sex. The "life expectancy" column (often written e_x) is the average number of years left.
2. Adjust for your country. Average lifespans differ by country, so the baseline moves up or down with your country's life expectancy.
3. Adjust for lifestyle. Smoking, activity, sleep, diet, weight, alcohol and similar factors move the estimate a little in either direction. We cap the total, so no set of answers gives an unrealistic result.
4. Add the years to your age. Your current age plus the adjusted years left is your estimated age at death. It is an average: about half of people live longer.

Worked example: a 70-year-old US man

The calculator then shifts this baseline for your country and applies the lifestyle steps described in section 3. For other ages, see our life expectancy by age table, or use the life expectancy calculator for a personal estimate.

Executive summary

Lifespan Check estimates life expectancy the same way retirement planners and public-health agencies do: starting from an actuarial life table for a person's age, sex and country, then applying evidence-informed, capped adjustments for lifestyle factors — smoking, alcohol, activity, sleep, diet, weight, stress, social connection, family history and check-up frequency. The output is a statistical, population-based estimate intended for education and self-reflection, not a medical or actuarial prediction for any one individual.

1. What an actuarial life table is

An actuarial life table is a structured dataset, built from real mortality records, that shows — for people of a given age and sex — the probability of surviving to the next year and the average number of years remaining. It's the same foundational tool used by the US Social Security Administration to set benefit schedules, by insurers to price policies, and by pension funds to plan payouts decades in advance. Lifespan Check starts every estimate from this same type of population baseline before any personalization happens.

Period vs cohort life expectancy

There are two kinds of life table. A period table uses the death rates observed in a single year and assumes they stay the same for the rest of a person's life. A cohort table follows people born in the same year and builds in projected changes in death rates over their lifetime. The two would only match if death rates never changed, which is extremely unlikely (ONS). Because death rates have usually fallen over time, cohort figures tend to be higher.

Lifespan Check uses the SSA's period table, the usual basis for published "life expectancy at age X" figures. If death rates keep improving, many people will live somewhat longer than a period estimate suggests.

2. Primary data sources

Where sources disagree slightly — which happens often in population health data — we favor the more conservative, less alarming figure and keep the total lifestyle adjustment capped, so no combination of answers can produce an unrealistic result in either direction.

3. Step by step: from baseline to your number

Step 1 — Age and sex baseline

We look up the actuarial baseline for someone of your exact age and sex: how many more years someone like you, on average, has left according to population data.

Step 2 — Country adjustment

Average life expectancy varies substantially by country, driven by factors like healthcare access, income levels, sanitation infrastructure and historical child-mortality rates. We shift the baseline to reflect your country's own life-expectancy data rather than using a single global average.

Step 3 — Lifestyle adjustments

Each lifestyle answer (smoking status, alcohol use, physical activity, sitting time, diet quality, sleep, stress/outlook, social connection, chronic conditions, family history, check-up frequency) applies a small, directional point adjustment based on the general direction and rough magnitude reported in population research. No single factor can swing the result dramatically — the combined effect is capped.

Step 4 — Final outputs

From the adjusted baseline we derive four figures: projected life expectancy, biological (body) age relative to chronological age, estimated healthy years remaining, and your probability of reaching age 100 (see step 5).

Step 5 — Survival odds, likely range and planning ages

An average hides a wide spread: some people die decades earlier and some live much longer. So the result also shows your chances of reaching 80, 85, 90 or 100, a likely range and two planning ages. We take the survivor column (l_x) of the US Social Security Administration 2023 period life table for your sex, start it at your current age, and shift the whole curve by the difference between your estimate and the table's average for your age. The likely range is the middle 50% of that curve (a 75% and a 25% chance of living past its two ends). The planning ages are the ages you have a 1-in-4 and a 1-in-10 chance of living past, which is a common way to choose how long savings must last.

For example, a 65-year-old US man with an average estimate (18.1 more years, to about 83) has a 64% chance of reaching 80, 24% of reaching 90 and about 1% of reaching 100. His likely range is 77–90, and his planning ages are 90 (1 in 4) and 94 (1 in 10). If his habits add 3 years to the estimate, his chance of reaching 90 rises to 37%. Because the table is a period table and the shift is a simplification, treat these odds as educational estimates, not a forecast.

4. Regional and global patterns

Some broad, well-established patterns show up consistently in public global life-expectancy data:

• Global average life expectancy at birth sits in the low-to-mid 70s, according to the most recent WHO and World Bank estimates.
• High-income regions — much of Western Europe, East Asia, Australia and North America — tend to average in the high-70s to mid-80s.
• Lower-income regions, particularly parts of Sub-Saharan Africa, still average meaningfully lower, though the global gap has narrowed substantially over the last several decades, driven largely by falling child mortality.
• Within any country, the gap between the healthiest and least healthy lifestyle profiles is typically far larger than the gap between countries.

Figures above are rounded, illustrative approximations of publicly reported WHO/World Bank data at the time of writing, not a live feed — always check primary sources (linked below) for exact current figures.

5. Limitations — what this calculator can't know

• It has no access to your genetics, medical records or diagnostic test results.
• It relies on self-reported answers, which are inherently approximate.
• It reflects population averages — half of any comparable group will outlive the estimate, often considerably.
• It cannot account for accidents, unforeseen medical events, or future medical advances.
• It is not a diagnostic tool, and its output should never replace professional medical or financial advice.

6. Glossary of life-table terms

The terms below appear in actuarial life tables and in our results. The examples come from the SSA 2023 period life table (2026 Trustees Report), which starts from 100,000 people born alive.

Sources: SSA Actuarial Life Table, 2023 period life table; WHO indicator metadata: healthy life expectancy (HALE).

7. Selected sources

• US Social Security Administration — Actuarial Life Table (2023 period life table, 2026 Trustees Report)
• Office for National Statistics (UK) — Period and cohort life expectancy explained
• World Bank — Life expectancy at birth, total (years)
• WHO — Global Health Observatory
• WHO — Indicator metadata: healthy life expectancy (HALE)
• CDC/NCHS — Life expectancy statistics

FAQ

This page is for educational and journalistic reference. It is not medical, financial or actuarial advice.