Castalia, OH has a population of 853 and is the 16,158th largest city in the United States. The population density is 817 per sq mi which is 217% higher than the Ohio average and 802% higher than the national average. The median age in Castalia is 46 which is approximately 16% higher than the Ohio average of 39. In Castalia, 61% of the population over 15 years of age are married, 95% speak English and 3% speak Spanish. 86% of Castalia residents were born in Ohio, 12% were born out of state, 0% were born outside of the United States and 2% were foreign born.