According to the United States Census Bureau, the township has a total area of 20.5 square miles, of which, 20.5 square miles of it is land and 0.1 square miles of it is water. It is drained by the Tohickon Creek eastward into the Delaware River. The township contains the villages of California, Paletown, Pullen, Quaker, Rich Hill, and Shelly. Natural features include Beaver Run, Dry Branch, Licking Run, Morgan Run, Rock Hill, and Tohickon Creek.
According to the Köppen climate classification system, Richland Township, Pennsylvania has a hot-summer, wet all year, humid continental climate. Dfa climates are characterized by at least one month having an average mean temperature ≤ 32.0 °F, at least four months with an average mean temperature ≥ 50.0 °F, at least one month with an average mean temperature ≥ 71.6 °F, and no significant precipitation difference between seasons. During the summer months, episodes of extreme heat and humidity can occur with heat index values ≥ 100 °F. On average, the wettest month of the year is July which corresponds with the annual peak in thunderstorm activity. During the winter months, episodes of extreme cold and wind can occur with wind chill values < 0 °F. The plant hardiness zone is 6b with an average annual extreme minimum air temperature of -2.0 °F. The average seasonal snowfall total is between 30 and 36 inches, and the average snowiest month is February which corresponds with the annual peak in nor'easter activity.
As of the census of 2000, there were 9,920 people, 3,763 households, and 2,667 families residing in the township. The population density was 484.7 people per square mile. There were 3,877 housing units at an average density of 189.4/sq mi. The racial makeup of the township was 96.35% White, 0.93% African American, 0.11% Native American, 1.16% Asian, 0.38% from other races, and 1.07% from two or more races. Hispanic or Latino of any race were 1.32% of the population. There were 3,763 households, out of which 34.9% had children under the age of 18 living with them, 59.3% were married couples living together, 7.7% had a female householder with no husband present, and 29.1% were non-families. 23.5% of all households were made up of individuals, and 11.1% had someone living alone who was 65 years of age or older. The average household size was 2.62 and the average family size was 3.13. In the township the population was spread out, with 26.2% under the age of 18, 6.5% from 18 to 24, 32.9% from 25 to 44, 20.7% from 45 to 64, and 13.8% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 97.8 males. For every 100 females age 18 and over, there were 94.8 males. The median income for a household in the township was $47,057, and the median income for a family was $55,359. Males had a median income of $37,677 versus $27,826 for females. The per capita income for the township was $19,582. About 2.5% of families and 5.4% of the population were below the poverty line, including 8.0% of those under age 18 and 6.4% of those age 65 or over.
