Waimalu, HI has a population of 13,478 and is the 3,105th largest city in the United States. The population density is 7,361 per sq mi which is 5679% higher than the Hawaii average and 8025% higher than the national average. The median age in Waimalu is 38 which is approximately 2% lower than the Hawaii average of 39. In Waimalu, 51% of the population over 15 years of age are married, 73% speak English and 2% speak Spanish. 57% of Waimalu residents were born in Hawaii, 18% were born out of state, 5% were born outside of the United States and 20% were foreign born.