Waipahu is located along the northern shore of both Middle Loch and West Loch of Pearl Harbor. It is a former sugar mill town.
The U.S. postal code for Waipahu is 96797 .
Waipahu is located at 21°23'33" North, 158°0'39" West (21.392500, -158.010710)1. Both Interstate H-1 and Farrington Highway (State Rte. 90) run east-west through the length of Waipahu. Waikele is located across the freeway north of Waipahu. To the west via either roadway can be reached Makakilo and Kapolei, with the Leeward coast beyond. To the east, lies Pearl City and the H-2 interchange to Waipi'o. At the western end of Waipahu is Kunia Road (State Rte. 750) which leads to the Waipahu newer growth areas of Royal Kunia and Village Park north of H-1, and eventuualy on up across the central plain to Kunia and Schofield Barracks, Wheeler Army Airfield, and Wahiawā. Kunia Road becomes Fort Weaver Road (State Rte. 76) south of Farrington Highway, and goes south to Honouliuli, Hawaii and 'Ewa.
According to the United States Census Bureau, the town has a total area of 6.8 km² (2.6 mi²). 6.7 km² (2.6 mi²) of it is land and 0.2 km² (0.1 mi²) of it is water. The total area is 2.28% water.
As of the census of 2000, there are 33,108 people, 7,566 households, and 6,431 families residing in the town. The population density is 4,974.0/km² (12,882.8/mi²). There are 8,033 housing units at an average density of 1,206.8/km² (3,125.7/mi²). The racial makeup of the town is 4.73% White, 0.93% African American, 0.14% Native American, 65.77% Asian, 12.31% Pacific Islander, 0.86% from other races, and 15.26% from two or more races. 6.09% of the population are Hispanic or Latino of any race.
There are 7,566 households out of which 36.2% have children under the age of 18 living with them, 59.8% are married couples living together, 18.1% have a female householder with no husband present, and 15.0% are non-families. 11.1% of all households are made up of individuals and 6.0% have someone living alone who is 65 years of age or older. The average household size is 4.23 and the average family size is 4.37.
In the town the population is spread out with 26.4% under the age of 18, 9.5% from 18 to 24, 26.8% from 25 to 44, 21.5% from 45 to 64, and 15.8% who are 65 years of age or older. The median age is 36 years. For every 100 females there are 97.6 males. For every 100 females age 18 and over, there are 95.3 males.
The median income for a household in the town is $49,444, and the median income for a family is $51,855. Males have a median income of $28,295 versus $23,818 for females. The per capita income for the town is $14,484. 13.8% of the population and 10.6% of families are below the poverty line. Out of the total people living in poverty, 17.0% are under the age of 18 and 13.9% are 65 or older.