[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Epidemiology](https://durgical.com/en/epidemiology/) › [Public health indicators](https://durgical.com/en/epidemiology/areas/indicators/) › Life expectancy

# Life expectancy

- Measure

How many years a person would live on average if, all through life, they faced the age-specific death rates of a given year.

Updated Nov 5, 2026

## Key points

- It is calculated with life tables from the age-specific death rates of a period (period life table).
- It does not predict how long a real newborn will live: it assumes current rates do not change.
- Infant deaths pull it down strongly; that is why life expectancy at 50 plus 50 exceeds life expectancy at birth.
- Healthy life expectancy (HALE) counts only the years lived in full health.
- It does not depend on the age structure of the population: countries can be compared without standardising.

On this page

- The basics Key points
- What it is
- Formula and reading
- Worked example
- Versions of life expectancy
- Markers
- How to read it
- Common pitfalls
- Memory aid

- Study Test yourself

- Connections Connections

## What it is

Life expectancy at birth is the average number of years a group of newborns would live if the age-specific death rates of a given year stayed the same throughout their lives. It is calculated from a life table built on age- and sex-specific rates. It also exists at any age (for example, at 60) and in a health-adjusted version: healthy life expectancy.

## Formula and reading

- Life expectancy at age x = years that, on average, remain for someone who reaches that age alive.
- In a closed cohort that has already died, life expectancy at birth is the mean age at death.
- In practice a period life table is used: probability of dying in each age interval, survivors and years lived.
- Healthy life expectancy = years expected in full health, given the mortality and morbidity of that year and place.

## Worked example

- A made-up group of 10 people born in the same year die at these ages: 1, 45, 60, 68, 72, 75, 78, 80, 84 and 87.
- Sum of ages at death: 650 years. Life expectancy at birth for this cohort: 650 / 10 = 65.0 years.
- Eight of them reached age 50 alive (all except those who died at 1 and 45).
- Years they had left: 10 + 18 + 22 + 25 + 28 + 30 + 34 + 37 = 204; 204 / 8 = 25.5 years of life expectancy at 50.
- Expected age at death for someone who turned 50: 50 + 25.5 = 75.5 years, more than the 65 at birth.
- If on average each person spent the equivalent of 7 years in poor health, healthy life expectancy would be about 65 − 7 = 58 years.
- Reading: one death in the first year pulls the average down a lot; better child survival raises life expectancy at birth.

## Versions of life expectancy

| Measure | What it counts | What it is for |
| --- | --- | --- |
| At birth | Average years from birth | Summary of a country's overall level of mortality |
| At a given age (for example, 60) | Years left for someone who reaches that age | Planning pensions and services for older adults |
| Healthy (HALE) | Years expected in full health | Seeing how much of life is spent ill or disabled |

## Markers

- e₀
- LE at birth
- HALE
- Life table

## How to read it

- The gap between total and healthy life expectancy shows the time lived with illness and disability, which is a load on services.
- Gaps in life expectancy between regions or social groups are an indicator of inequity.

## Common pitfalls

- Reading life expectancy at birth as the age at which most people die: high infant mortality lowers the average even when many adults live long.
- Believing a newborn today will live exactly that many years: the table assumes fixed rates.
- Confusing life expectancy with the maximum human lifespan.

## Memory aid

Life expectancy looks ahead with today's rates: a snapshot of the present, not a prophecy.

## Test yourself

Think of the answer, then tap the question to see it.

## What data are used to calculate a country's life expectancy at birth?

A life table based on the age- and sex-specific death rates of a year or period.

## Why can life expectancy at 50 plus 50 exceed life expectancy at birth?

Because someone who reached 50 has already survived the deaths of childhood and youth, which pull the average at birth down.

## What does healthy life expectancy add?

It discounts the years lived in poor health: it counts only the years expected in full health.

## Does life expectancy need age standardisation to compare countries?

No: it is built from age-specific rates, so it does not depend on the age structure of the population.

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## Connections

## Related 6

- [Mortality rates: crude and specific](https://durgical.com/en/epidemiology/mortality-rates-crude-and-specific/)
- [Actuarial life tables](https://durgical.com/en/epidemiology/actuarial-life-tables/)
- [Disability-adjusted life years (DALYs)](https://durgical.com/en/epidemiology/disability-adjusted-life-years/)
- [Demographic transition and the population pyramid](https://durgical.com/en/epidemiology/demographic-transition-and-the-population-pyramid/)
- [Years of potential life lost](https://durgical.com/en/epidemiology/years-of-potential-life-lost/)
- [Quality-adjusted life years (QALYs)](https://durgical.com/en/epidemiology/quality-adjusted-life-years/)

[← All of epidemiology](https://durgical.com/en/epidemiology/)

Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.

Sources: [Life expectancy](https://www.who.int/data/gho/indicator-metadata-registry/imr-details/65) (World Health Organization, 2026); [Healthy life expectancy (HALE)](https://www.who.int/data/gho/indicator-metadata-registry/imr-details/66) (World Health Organization, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/epidemiology/life-expectancy/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/epidemiology/life-expectancy/