Greenfield, OH has a population of 4,794 and is the 6,645th largest city in the United States. The population density is 2,306 per sq mi which is 795% higher than the Ohio average and 2445% higher than the national average. The median age in Greenfield is 38 which is approximately 3% lower than the Ohio average of 39. In Greenfield, 52% of the population over 15 years of age are married, 99% speak English and 1% speak Spanish. 90% of Greenfield residents were born in Ohio, 10% were born out of state, 0% were born outside of the United States and 0% were foreign born.