Clermont County is part of the Cincinnati–Middletown, OH-KY-IN Metropolitan Statistical Area.
As of the census of 2000, there were 177,977 people, 66,013 households, and 49,047 families residing in the county. The population density was 394 people per square mile (152/km²). There were 69,226 housing units at an average density of 153 per square mile (59/km²). The racial makeup of the county was 97.13% White, 0.91% African American, 0.19% Native American, 0.63% Asian, 0.02% Pacific Islander, 0.26% from other races, and 0.86% from two or more races. 0.87% of the population were Hispanic or Latino of any race. 32.7% were of German, 16.7% American, 12.0% Irish and 11.0% English ancestry according to Census 2000.
There were 66,013 households out of which 38.10% had children under the age of 18 living with them, 60.40% were married couples living together, 10.00% had a female householder with no husband present, and 25.70% were non-families. 21.00% of all households were made up of individuals and 7.00% had someone living alone who was 65 years of age or older. The average household size was 2.67 and the average family size was 3.11.
In the county the population was spread out with 27.90% under the age of 18, 8.40% from 18 to 24, 31.70% from 25 to 44, 22.60% from 45 to 64, and 9.40% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 96.40 males. For every 100 females age 18 and over, there were 93.60 males.
The median income for a household in the county was $49,386, and the median income for a family was $57,032. Males had a median income of $40,739 versus $27,613 for females. The per capita income for the county was $22,370. About 5.30% of families and 7.10% of the population were below the poverty line, including 8.70% of those under age 18 and 7.90% of those age 65 or over.