Since these figures are not directly available via Google search, I calculated them using the mid-year population estimates from the World population Prospects (WPP) 2024:
World population: In 2024, the World population is estimated at 8.2 billion (8,162 million). The population is projected to peak in 2084 at 10.3 billion.
Children Under 5 Years Old: The number of children under 5 is 647 million in 2024. This figure peaked in 2017 at 698 million and is projected to decline to 550 million by 2100.
Children Aged 0–14 Years: The population of children aged 0–14 peaked in 2020 and stands at 2.0 billion in 2024.
Children and Adolescents under 18: The population of those aged 0–17 years peaked in 2022 and stands at 2.4 billion (2,413 million) in 2024.
Children and Adolescents under 20: The population of those aged 0–19 years is 2.7 billion (2,668 million) in 2024, which marks the peak year for this age group.
Population Under 25 Years Old (0–24): The number of people aged 0–24 years is 3.3 billion in 2024. This population is expected to experience a slight increase and peak in 2030.
Table of the World population under 5, 10, 15, 18, 20, and 25 years old (in million)
| Population | Age Group | 2015 | 2020 | 2025 | 2030 | 2050 | 2100 |
|---|---|---|---|---|---|---|---|
| Under 5 years old | 0-4 | 696 | 683 | 644 | 645 | 656 | 550 |
| Under 10 years old | 0-9 | 1,358 | 1,374 | 1,321 | 1,283 | 1,316 | 1,110 |
| Under 15 years old | 0-14 | 1,988 | 2,035 | 2,008 | 1,958 | 1,969 | 1,681 |
| Under 18 years old | 0-17 | 2,355 | 2,413 | 2,409 | 2,370 | 2,357 | 2,030 |
| Under 20 years old | 0-19 | 2,597 | 2,662 | 2,667 | 2,643 | 2,613 | 2,265 |
| Under 25 years old | 0-24 | 3,206 | 3,267 | 3,291 | 3,303 | 3,251 | 2,866 |
Also by sex:
World population
Source: World population Prospects (WPP) 2024. Population on 01 July, by 1-year age groups.