Kailua, HI has a population of 38,514 and is the 1,080th largest city in the United States. The population density is 4,968 per sq mi which is 3800% higher than the Hawaii average and 5383% higher than the national average. The median age in Kailua is 43 which is approximately 12% higher than the Hawaii average of 39. In Kailua, 60% of the population over 15 years of age are married, 89% speak English and 2% speak Spanish. 50% of Kailua residents were born in Hawaii, 39% were born out of state, 3% were born outside of the United States and 9% were foreign born.