The U.S. postal code for Waipi'o is 96797
Waipi'o is located at 21°25'5" North, 157°59'53" West (21.418050, -157.997988)1, south of Mililani Town via either Interstate H-2 or Kamehameha Highway (State Rte. 99). The town is immediately east of Waikele, separated by Kamehameha Highway, the road that leads southward to Farrington Highway (State Rte. 90) with connections then to Pearl City to the east and Waipahu to the west. In this same area south of Waipi'o is the interchange between Hawai'i Interstates H-1 and H-2.
As of the census of 2000, there were 11,672 people, 3,974 households, and 2,873 families residing in the town. The population density was 3,755.5/km² (9,700.5/mi²). There were 4,110 housing units at an average density of 1,322.4/km² (3,415.8/mi²). The racial makeup of the town was 14.42% White, 2.82% African American, 0.18% Native American, 54.66% Asian, 5.45% Pacific Islander, 0.86% from other races, and 21.62% from two or more races. 6.76% of the population were Hispanic or Latino of any race.
There were 3,974 households out of which 38.6% have children under the age of 18 living with them, 57.1% are married couples living together, 10.5% have a female householder with no husband present, and 27.7% are non-families. 20.9% of all households are made up of individuals and 2.2% have someone living alone who is 65 years of age or older. The average household size is 2.92 and the average family size is 3.41.
In the town the population is spread out with 26.2% under the age of 18, 9.3% from 18 to 24, 34.6% from 25 to 44, 23.4% from 45 to 64, and 6.5% who are 65 years of age or older. The median age is 34 years. For every 100 females there are 101.1 males. For every 100 females age 18 and over, there are 100.0 males.
The median income for a household in the town is $61,276, and the median income for a family is $69,282. Males have a median income of $41,943 versus $31,840 for females. The per capita income for the town is $24,451. 4.1% of the population and 3.3% of families are below the poverty line. Out of the total people living in poverty, 5.1% are under the age of 18 and 7.0% are 65 or older.