A 17-Year-Old in 1900: Which Grade Today Is Just as Tall? 125 Years of Height | Data in Motion #04

How tall was a 17-year-old in 1900, compared with schoolchildren today? Using Japan's national school checkup records (1900–2025), estimates for 200 countries and territories, and Japan's national fitness test, we watch how height, weight, body shape and fitness have changed — with figures that grow, shrink and change places.

Height and weight in Japan's school records

These are national averages for students measured at school checkups. “Today” means the 2025 school year.

Both averages first reached their highest recorded level in 1994. There are no national figures for school years 1921 or 1940–1947. Measurements for 2020–2023 include a different time of year and cannot be compared with other years (striped in the video).

Grade numbers use the US convention: Japan's first and second years of junior high correspond to Grades 7 and 8; the last year of elementary school is Grade 6.

World height estimates

These estimates describe average height at age 18. The years are years of birth. They are estimates based on data; this episode includes no future projections. They come from a separate dataset from Japan's school measurements at age 17.

Heights are in cm, rounded to one decimal place. Ranks order all 200 countries and territories from tallest to shortest by the central estimate. The median is the middle of those country and territory estimates.

The men's lead passes from Sweden to Iceland (birth years 1912 onward), then the Netherlands (1958 onward). For women, it passes from Sweden to Iceland (1914 onward), the Netherlands (1957 onward), then Latvia (1986 onward). The small differences at these changes fall within the estimates' uncertainty ranges.

Japan's gain between the 1896 and 1996 birth groups was 14.7 cm for men (fifth-largest) and 16.0 cm for women (second-largest). Gains were calculated from the underlying data, so they can differ from subtracting the rounded heights shown here.

Adult BMI shares (estimates)

Body mass index (BMI) is weight in kg divided by height in meters squared, used as a guide to body shape. These estimates cover adults aged 20 and older, adjusted to the same age distribution to allow comparisons across places and years. Each cell shows 1980 → 2024, in percent.

The share of Japanese men with BMI 25 or higher rose from 16.5% to 34.0%. In 2024, the estimated share of Japanese women with BMI under 18.5 was 16.6%, ninth-highest among 200 countries and territories. WHO's threshold for adult obesity is BMI 30; Japan's checkups use 25 under the Japan Society for the Study of Obesity's criteria.

Percentages are rounded to one decimal place and may not sum to 100%. The video's groups of 100 people use whole numbers adjusted to total exactly 100.

Sitting height and chest measurements at school

Sitting height measures the distance from the seat to the top of the head. Height minus sitting height gives an approximate measure of leg length.

Chest circumference is the measurement around the chest. It stopped being a required school checkup item in 1995. Sitting height and tests for parasite eggs stopped being required in 2016.

Fitness and school checkups

Each fitness cell shows the average in school year 1999 → 2025. Grip strength is a guide to muscle strength.

What this episode shows

• In Japan's school records for 1900, boys aged 17 fall between the 2025 averages for boys in Grades 7 and 8; girls aged 17 are close to the average for girls in Grade 6.
• Height at age 17 in Japan has barely changed since 1994; in world height estimates, Japan rose from #187 to #102 for men and #195 to #112 for women between the 1896 and 1996 birth groups.
• Among Japanese adults, BMI 25 or higher became more common for men, while BMI under 18.5 became more common for women; grip strength fell among children and young adults but rose at ages 65–79.