If every person on Earth stood on the head of the person below, the stack would be about 13 million kilometers (8 million miles) tall. The stack is imaginary, so its height is a calculation, not a measurement. It multiplies the number of people alive in 2026 by their average height.

Size

The United Nations estimates that about 8.3 billion people are alive in 2026. If every one of them were 1.7 meters (5 feet 7 inches) tall, the stack would be about 14 million kilometers tall. But about a quarter of all people are children under 15, and many adults are shorter than that.

A closer estimate uses the average height at each age. Growth charts from the World Health Organization give the heights of babies and young children. A worldwide study by the NCD Risk Factor Collaboration, a network of health scientists, gives average heights for ages 5 to 19. In 2019, 19-year-olds averaged 171 centimeters (5 feet 7 inches) for young men and 159 centimeters (5 feet 2 inches) for young women.

For adults, the calculation uses the height each generation had reached at age 19. Combining all these heights with the United Nations' count of people at each age gives an average of about 1.5 meters (5 feet) for everyone alive, from newborns to the oldest adults. Multiplying 8.3 billion people by that average gives about 13 million kilometers. The result is an estimate, so it is rounded to the nearest million kilometers.

Size comparisons

The stack would be about as tall as 1,000 Earths piled on top of each other.
It would reach about 33 times as far as the distance from Earth to the Moon, which is 384,400 kilometers (238,900 miles).
It would cover about one-twelfth of the distance from Earth to the Sun, about 150 million kilometers.
It would be about as tall as nine Suns stacked up, and about three-quarters the width of the larger of the two giant stars in Capella, the next larger object in the explorer.
A car driving at a steady 100 kilometers per hour (62 miles per hour), without ever stopping, would take about 14 years to travel the height of the stack.

A growing stack

The stack grows as the world's population grows. The United Nations estimates that there were 8.2 billion people in 2024. It expects the number to peak at about 10.3 billion in the mid-2080s and then fall slightly, to 10.2 billion by 2100. If the average height stayed about 1.5 meters, a stack of 10.3 billion people would be about 16 million kilometers tall.

Why it could never be built

A real stack of people would collapse long before it grew tall, because each person would have to hold up everyone above. A 2012 study estimated that in 2005 the world's adults weighed about 62 kilograms (137 pounds) each, on average. A column of only 100 adults would press down on the person beneath them with 6.2 tonnes (13,700 pounds).

The same study estimated that all the world's adults together weighed about 287 million tonnes in 2005. Even if people could bear such weight, nearly all of the stack would be out in space, far beyond the Moon.

Sources

World Population Prospects 2024: Summary of Results. United Nations Department of Economic and Social Affairs, 2024.
World Population Prospects 2024: Population by five-year age group and sex. United Nations Department of Economic and Social Affairs, 2024.
Child Growth Standards: Length/height-for-age. World Health Organization.
Height: data downloads. NCD Risk Factor Collaboration, 2020.
The weight of nations: an estimation of adult human biomass. Walpole et al., BMC Public Health, 2012.
Capella (α Aurigae) revisited: New binary orbit, physical properties, and evolutionary state. Torres et al., The Astrophysical Journal, 2015.
Earth Fact Sheet. NASA, 2024.
Moon Fact Sheet. NASA, 2024.
Sun Fact Sheet. NASA, 2024.

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