The map above shows Illinois and Ohio side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Illinois vs Ohio Geography
Land area: Illinois has a land area of 55,513 square miles (143,778 km²), while Ohio has 40,859 square miles (105,824 km²). Illinois' land area is 1.4 times (36%) larger than Ohio's.
Total area: Illinois: 57,913 square miles (149,995 km²) vs Ohio: 44,826 square miles (116,098 km²), including inland and coastal water. Illinois' total area is 1.3 times (29%) larger than Ohio's.
Length: Illinois is 390 miles (628 km) long from north to south; Ohio is 291 miles (468 km). Illinois' north-south length is 1.3 times (34%) longer than Ohio's.
Width: Illinois spans 283 miles (456 km) east to west; Ohio spans 317 miles (510 km). Ohio's east-west width is 1.1 times (12%) wider than Illinois'.
Highest point: Illinois's highest point is Charles Mound at 1,232 feet (376 m); Ohio's is Campbell Hill at 1,547 feet (472 m). Campbell Hill is 315 feet higher than Charles Mound.
Lowest point: Illinois's lowest point is Mississippi River at 292 feet; Ohio's is Ohio River at 455 feet. Illinois's lowest point is 163 feet lower.
Illinois vs Ohio Population and History
Population: Illinois has a population of 12,710,158 (2024), while Ohio has 11,883,304 (2024). Illinois' population is 1.1 times (7%) larger than Ohio's.
Population density: Illinois: 229.0 people per square mile vs Ohio: 290.8. Ohio's population density is 1.3 times (27%) higher than Illinois'.
Biggest city: Illinois's biggest city is Chicago with 2,721,308 people; Ohio's is Columbus with 933,263. Chicago's population is 2.9 times (192%) larger than Columbus'.
Largest metro area: Illinois's largest metropolitan area is Chicago-Naperville-Elgin, IL-IN metro area (9,408,576 people) vs Ohio's Cincinnati, OH-KY-IN metro area (2,302,815). Chicago-Naperville-Elgin, IL-IN metro area's population is 4.1 times (309%) larger than Cincinnati, OH-KY-IN metro area's.
History: Illinois: Admitted to the Union on December 3, 1818, as the 21st state. Ohio: Admitted to the Union on March 1, 1803, as the 17th state. In its current form, Ohio is the older of the two by 15 years.
Illinois vs Ohio Economy
GDP: Illinois's GDP is $1,148.1 billion (2024) vs Ohio's $923.1 billion. Illinois' economic output is 1.2 times (24%) larger than Ohio's.
GDP per capita: Illinois: $90,330 per person vs Ohio: $77,684. Illinois' GDP per capita is 1.2 times (16%) higher than Ohio's.
Average income: Illinois: $74,522 vs Ohio: $64,464 average income per person (per capita personal income). Illinois' average income is 1.2 times (16%) higher than Ohio's.
Illinois vs Ohio Counties
Number of counties: Illinois has 102 counties, while Ohio has 88. Illinois' county count is 1.2 times (16%) higher than Ohio's.
Biggest county by area: Illinois's largest county is McLean County at 1,183 square miles; Ohio's is Ashtabula County at 702 square miles. McLean County's land area is 1.7 times (68%) larger than Ashtabula County's.
Smallest county by area: Illinois: Putnam County (160 sq mi) vs Ohio: Lake County (229 sq mi). Lake County's land area is 1.4 times (43%) larger than Putnam County's.
Most populous county: Illinois: Cook County (5,182,617 people) vs Ohio: Franklin County (1,356,303 people). Cook County's population is 3.8 times (282%) larger than Franklin County's.
Least populous county: Illinois: Hardin County (3,550 people) vs Ohio: Vinton County (12,545 people). Vinton County's population is 3.5 times (253%) larger than Hardin County's.
Richest county: Illinois: Cumberland County ($104,890 per capita income) vs Ohio: Delaware County ($96,573). Cumberland County's income is 1.1 times (9%) richer than Delaware County's.
Poorest county: Illinois: Lawrence County ($43,606 per capita income) vs Ohio: Noble County ($34,940). Lawrence County's income is 1.2 times (25%) richer than Noble County's.
Illinois vs Ohio Taxes
State income tax: Illinois has a top income tax rate of 4.95%, while Ohio has a top income tax rate of 2.75%. Illinois's top rate is 2.2 percentage points higher.
Property tax: Illinois: 1.92% effective rate vs Ohio: 1.22% of home value per year. Illinois's rate is 0.7 percentage points higher.
Sales tax: Illinois: 8.98% combined state and average local rate vs Ohio: 7.29%. Illinois's combined rate is 1.69 percentage points higher.
Official Websites
Illinois official website · Ohio official website
More Size Comparisons
All Illinois size comparisons · All Ohio size comparisons
Area, elevation and boundary figures come from official national statistics and US Census Bureau and Natural Earth boundary data; US state population, economic, county and tax figures come from the US Census Bureau, the Bureau of Economic Analysis and the Tax Foundation. Figures are rounded and for general reference.