Counties in Illinois by average household size
Calhoun County had the highest average household size of 102 counties in 2021, at 3.5 persons per household. Jackson County had the lowest, at 2.2 persons per household. The median was 2.4 persons per household and the figure for Illinois was 2.5 persons per household. Source: the U.S. Census Bureau.
Map of counties, 2021
- Under 2.3
- 2.3 to 2.4
- 2.4 to 2.5
- 2.5 to 2.6
- 2.6 and over
Top 40 counties, 2021
Full ranking
Other periods
About this ranking
Average number of persons per private household. EU countries: EU-SILC. United States: American Community Survey five-year estimate of people in households divided by occupied housing units, where the period shown is the last year of the five-year span.
Covers private households only; people living in institutions or other group quarters are excluded. EU-SILC figures refer to the survey year. The EU and US surveys differ, so their figures are not strictly comparable.
Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. Equal values share a rank.
How to cite
U.S. Census Bureau. American Community Survey 5-year estimates, table B25010: average household size of occupied housing units. https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat. Retrieved 2026-10-12.Citation styles
APA 7
U.S. Census Bureau. (2026). American Community Survey 5-year estimates, table B25010: average household size of occupied housing units (Counties in Illinois by average household size, 2021) [Data set]. Retrieved October 12, 2026, from https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat
MLA 9
American Community Survey 5-year estimates, table B25010: average household size of occupied housing units, Counties in Illinois by average household size, 2021. U.S. Census Bureau, 29 Jan. 2026, https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat. Invokely, https://invokely.ai/rankings/average-household-size/illinois-counties?period=2021. Accessed 12 Oct. 2026.
Chicago (author-date)
U.S. Census Bureau. 2026. American Community Survey 5-year estimates, table B25010: average household size of occupied housing units. Counties in Illinois by average household size, 2021. Dataset. Accessed October 12, 2026. https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat. Also distributed by Invokely, https://invokely.ai/rankings/average-household-size/illinois-counties?period=2021.
Harvard
U.S. Census Bureau (2026) American Community Survey 5-year estimates, table B25010: average household size of occupied housing units, Counties in Illinois by average household size, 2021 [Dataset]. Available at: https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat, via Invokely: https://invokely.ai/rankings/average-household-size/illinois-counties?period=2021 (Accessed: 12 October 2026).
BibTeX
@misc{census_counties_in_illinois_by_2021,
author = {{U.S. Census Bureau}},
title = {{American Community Survey 5-year estimates, table B25010: average household size of occupied housing units: Counties in Illinois by average household size, 2021}},
year = {2026},
howpublished = {Data set},
url = {https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat},
urldate = {2026-10-12},
note = {Accessed via Invokely, https://invokely.ai/rankings/average-household-size/illinois-counties?period=2021. Publisher attribution: U.S. Census Bureau. American Community Survey 5-year estimates, table B25010: average household size of occupied housing units. https://www2.census.gov/programs-surveys/acs/summary\_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat. Retrieved 2026-10-12.},
}
RIS
TY - DATA
AU - U.S. Census Bureau
TI - American Community Survey 5-year estimates, table B25010: average household size of occupied housing units: Counties in Illinois by average household size, 2021
PY - 2026
DA - 2026/01/29
PB - U.S. Census Bureau
DB - Invokely
UR - https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat
L2 - https://invokely.ai/rankings/average-household-size/illinois-counties?period=2021
Y2 - 2026/10/12
N1 - Accessed via Invokely, https://invokely.ai/rankings/average-household-size/illinois-counties?period=2021.
N1 - Publisher attribution: U.S. Census Bureau. American Community Survey 5-year estimates, table B25010: average household size of occupied housing units. https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b25010.dat. Retrieved 2026-10-12.
ER -
Use this data in your AI agent
Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:
Rank Counties in Illinois by average household size using official data, and cite the source.
rank_places {"indicator":"average_household_size","level":"province","within":"Illinois","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=average_household_size&level=province&within=Illinois&limit=10Questions
Which county has the highest average household size?
Calhoun County, with 3.5 persons per household in 2021, according to the U.S. Census Bureau.
Which county has the lowest average household size?
Jackson County, with 2.2 persons per household in 2021.
Where does this ranking come from?
Every value comes from one source and one period, so the places are comparable: U.S. Census Bureau, American Community Survey 5-year estimates, table B25010: average household size of occupied housing units. Retrieved 2026-10-12.
Average household size: other rankings
- Counties in New York
- Counties in Alabama
- Counties in Missouri
- Cities in Alabama
- Cities in Maryland
- Cities in Connecticut