According to the United States Census Bureau, the city has a total area of 104.1 km² (40.2 mi²). 103.8 km² (40.1 mi²) of it is land and 0.3 km² (0.1 mi²) of it is water. The total area is 0.32% water.
Tempe contains the main campus of Arizona State University.
As of the census2 of 2000, there are 158,625 people, 63,602 households, and 33,645 families residing in the city. The population density is 1,528.8/km² (3,959.4/mi²). There are 67,068 housing units at an average density of 646.4/km² (1,674.1/mi²). The racial makeup of the city is 77.51% White, 3.66% Black or African American, 2.01% Native American, 4.75% Asian, 0.29% Pacific Islander, 8.49% from other races, and 3.30% from two or more races. 17.95% of the population are Hispanic or Latino of any race.
There are 63,602 households out of which 24.4% have children under the age of 18 living with them, 38.4% are married couples living together, 9.7% have a female householder with no husband present, and 47.1% are non-families. 28.5% of all households are made up of individuals and 4.6% have someone living alone who is 65 years of age or older. The average household size is 2.41 and the average family size is 3.05.
In the city the population is spread out with 19.8% under the age of 18, 21.3% from 18 to 24, 33.2% from 25 to 44, 18.5% from 45 to 64, and 7.2% who are 65 years of age or older. The median age is 29 years. For every 100 females there are 106.9 males. For every 100 females age 18 and over, there are 107.1 males.
The median income for a household in the city is $42,361, and the median income for a family is $55,237. Males have a median income of $36,406 versus $28,605 for females. The per capita income for the city is $22,406. 14.3% of the population and 7.5% of families are below the poverty line. Out of the total people living in poverty, 13.6% are under the age of 18 and 5.1% are 65 or older.