Wainaku, HI has a population of 1,293 and is the 13,584th largest city in the United States. The population density is 979 per sq mi which is 669% higher than the Hawaii average and 981% higher than the national average. The median age in Wainaku is 47 which is approximately 21% higher than the Hawaii average of 39. In Wainaku, 58% of the population over 15 years of age are married, 78% speak English and 0% speak Spanish. 58% of Wainaku residents were born in Hawaii, 24% were born out of state, 1% were born outside of the United States and 17% were foreign born.