Niles, OH has a population of 18,877 and is the 2,316th largest city in the United States. The population density is 2,192 per sq mi which is 751% higher than the Ohio average and 2319% higher than the national average. The median age in Niles is 42 which is approximately 8% higher than the Ohio average of 39. In Niles, 50% of the population over 15 years of age are married, 97% speak English and 1% speak Spanish. 82% of Niles residents were born in Ohio, 17% were born out of state, 1% were born outside of the United States and 1% were foreign born.