Waikapu, HI has a population of 3,266 and is the 8,377th largest city in the United States. The population density is 296 per sq mi which is 133% higher than the Hawaii average and 227% higher than the national average. The median age in Waikapu is 37 which is approximately 4% lower than the Hawaii average of 39. In Waikapu, 61% of the population over 15 years of age are married, 80% speak English and 3% speak Spanish. 56% of Waikapu residents were born in Hawaii, 27% were born out of state, 2% were born outside of the United States and 15% were foreign born.