Population under 18 in Ontario County

Population under 18 in Ontario County was 18.4% in 2025, according to the U.S. Census Bureau. That is down 0.3 pts from 2024. That is the 39th highest of 62 counties in 2025.

202518.4%

Change on 2024-0.3 pts

Rank39th of 62Counties in New York ranked

Series high22.42010

Series low18.42025

Next release: Friday, 25 June 2027, estimated by Invokely from past publication dates (low confidence), not announced by the publisher. Release calendar

Population under 18 in Ontario County, 2010 to 2025

%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12, published 2026-06-25.

All 16 values

Period	%
2025	18.4
2024	18.7
2023	19
2022	19.2
2021	19.3
2020	19.7
2019	19.8
2018	20.2
2017	20.4
2016	20.6
2015	20.7
2014	21
2013	21.2
2012	21.6
2011	22
2010	22.4

Compared with New York and United States

Place	2025
Ontario County	18.4
New York	19.5
United States	21.1

Rankings

US states by population under 18 51 places
Counties in New York by population under 18 62 places

Definition

Residents aged 0 to 17 as a percentage of total population on 1 July. United States: Census Bureau county population estimates by age; states and the nation are sums of their counties.

Uses the US age of majority. Not comparable with population_0_14_share, which stops at 14.

How to cite

U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Census Bureau. (2026). Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties (Population under 18, Ontario County, 2010 to 2025) [Data set]. Retrieved October 12, 2026, from https://www.census.gov/programs-surveys/popest/data/data-sets.html

MLA 9

Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties, Population under 18, Ontario County, 2010 to 2025. U.S. Census Bureau, 25 June 2026, https://www.census.gov/programs-surveys/popest/data/data-sets.html. Invokely, https://invokely.ai/en/population-under-18/ontario-county-new-york. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Census Bureau. 2026. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. Population under 18, Ontario County, 2010 to 2025. Dataset. Accessed October 12, 2026. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Also distributed by Invokely, https://invokely.ai/en/population-under-18/ontario-county-new-york.

Harvard

U.S. Census Bureau (2026) Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties, Population under 18, Ontario County, 2010 to 2025 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/en/population-under-18/ontario-county-new-york (Accessed: 12 October 2026).

BibTeX

@misc{census_population_under_18_ontario_2025,
  author = {{U.S. Census Bureau}},
  title = {{Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties: Population under 18, Ontario County, 2010 to 2025}},
  year = {2026},
  howpublished = {Data set},
  url = {https://www.census.gov/programs-surveys/popest/data/data-sets.html},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/en/population-under-18/ontario-county-new-york. Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.},
}

RIS

TY  - DATA
AU  - U.S. Census Bureau
TI  - Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties: Population under 18, Ontario County, 2010 to 2025
PY  - 2026
DA  - 2026/06/25
PB  - U.S. Census Bureau
DB  - Invokely
UR  - https://www.census.gov/programs-surveys/popest/data/data-sets.html
L2  - https://invokely.ai/en/population-under-18/ontario-county-new-york
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/population-under-18/ontario-county-new-york.
N1  - Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.
ER  -

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Questions

What is the population under 18 in Ontario County?

Population under 18 in Ontario County was 18.4% in 2025, according to the U.S. Census Bureau. That is down 0.3 pts from 2024. That is the 39th highest of 62 counties in 2025.

Where does this figure come from?

U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. Retrieved by Invokely on 2026-10-12.

What was the highest population under 18 in Ontario County?

22.4% in 2010, the highest value since 2010 in this series.

Related statistics for Ontario County

All statistics for Ontario County | Ontario County in figures