Waimalu is a census-designated place (CDP) in Honolulu County, Hawaiʻi, United States. The population was 13,730 at the 2010 census.
Waimalu is located at 21°23′57″N 157°56′54″W / 21.39917°N 157.94833°W / 21.39917; -157.94833 (21.399150, -157.948432).
According to the United States Census Bureau, the CDP has a total area of 1.9 square miles (5.0 km), of which 1.8 square miles (4.7 km) is land and 0.077 square miles (0.2 km), or 4.62%, is water.
As of the census of 2000, there were 29,371 people, 10,524 households, and 7,514 families residing in the CDP. The population density was 4,972.1 people per square mile (1,918.8/km²). There were 10,999 housing units at an average density of 1,862.0 per square mile (718.6/km²). The racial makeup of the CDP was 17.08% White, 2.33% African American, 0.26% Native American, 55.32% Asian, 5.63% Pacific Islander, 1.10% from other races, and 18.27% from two or more races. Hispanic or Latino of any race were 5.97% of the population.
There were 10,524 households out of which 29.2% had children under the age of 18 living with them, 55.9% were married couples living together, 11.1% had a female householder with no husband present, and 28.6% were non-families. 21.0% of all households were made up of individuals and 3.4% had someone living alone who was 65 years of age or older. The average household size was 2.78 and the average family size was 3.26.
In the CDP the population was spread out with 21.4% under the age of 18, 9.5% from 18 to 24, 31.5% from 25 to 44, 27.5% from 45 to 64, and 10.1% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 102.6 males. For every 100 females age 18 and over, there were 102.7 males.
The median income for a household in the CDP was $61,210, and the median income for a family was $70,740. Males had a median income of $40,949 versus $32,090 for females. The per capita income for the CDP was $25,913. About 4.1% of families and 5.9% of the population were below the poverty line, including 7.9% of those under age 18 and 3.0% of those age 65 or over.