For someone born in 1820, the life expectancy at birth was roughly 26 years globally , but that number was heavily pulled down by very high infant and child mortality. Once a person survived early childhood, their expected lifespan was much longer than 26 years.

What that means

  • At birth: about 26 years worldwide in 1820.
  • If they survived infancy: their remaining life expectancy would have been substantially higher, because early deaths were so common.
  • By comparison: later 19th-century data from England and Wales show life expectancy at birth around 40 years in the 1871–1880 decade, illustrating how much conditions improved over time.

Important context

A single number can be misleading here. In 1820, life expectancy was not a prediction for every individual; it was an average shaped by epidemics, poor sanitation, limited medicine, and especially infant mortality.

Practical takeaway

If you want the simplest answer: around 26 years at birth , with a much better chance of living far longer if childhood was survived.