As of the census of 2000, there were 248,399 people, 93,382 households, and 67,701 families residing in the county. The population density was 177 people per square mile (68/km²). There were 107,302 housing units at an average density of 76 per square mile (30/km²). The racial makeup of the county was 88.59% White, 0.82% Black or African American, 0.89% Native American, 2.95% Asian, 0.16% Pacific Islander, 3.39% from other races, and 3.21% from two or more races. 9.67% of the population were Hispanic or Latino of any race. 15.5% were of German, 12.3% English, 10.6% Irish, 7.1% Italian and 7.0% American ancestry according to Census 2000. 89.7% spoke English and 6.0% Spanish as their first language.
There were 93,382 households out of which 35.30% had children under the age of 18 living with them, 59.40% were married couples living together, 9.20% had a female householder with no husband present, and 27.50% were non-families. 21.30% of all households were made up of individuals and 8.10% had someone living alone who was 65 years of age or older. The average household size was 2.63 and the average family size was 3.06.
In the county the population was spread out with 26.50% under the age of 18, 6.90% from 18 to 24, 29.00% from 25 to 44, 24.50% from 45 to 64, and 13.10% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 96.40 males. For every 100 females age 18 and over, there were 93.90 males.
The median income for a household in the county was $57,535, and the median income for a family was $65,858 (these figures had risen to $68,463 and $80,987 respectively as of a 2007 estimate). Males had a median income of $50,410 versus $33,763 for females. The per capita income for the county was $27,963. About 3.90% of families and 5.80% of the population were below the poverty line, including 6.30% of those under age 18 and 3.80% of those age 65 or over.
There are three general aviation airports in Placer County:
The closest commercial airport is Sacramento International Airport in Sacramento.