Northfield, OH has a population of 3,679 and is the 7,818th largest city in the United States. The population density is 3,408 per sq mi which is 1223% higher than the Ohio average and 3662% higher than the national average. The median age in Northfield is 37 which is approximately 6% lower than the Ohio average of 39. In Northfield, 49% of the population over 15 years of age are married, 90% speak English and 1% speak Spanish. 79% of Northfield residents were born in Ohio, 14% were born out of state, 0% were born outside of the United States and 7% were foreign born.