Waipahu, HI has a population of 41,590 and is the 984th largest city in the United States. The population density is 15,697 per sq mi which is 12224% higher than the Hawaii average and 17225% higher than the national average. The median age in Waipahu is 37 which is approximately 4% lower than the Hawaii average of 39. In Waipahu, 56% of the population over 15 years of age are married, 48% speak English and 0% speak Spanish. 49% of Waipahu residents were born in Hawaii, 6% were born out of state, 4% were born outside of the United States and 40% were foreign born.