Clayton, NJ has a population of 8,386 and is the 4,528th largest city in the United States. The population density is 1,185 per sq mi which is 118435% higher than the New Jersey average and 1208% higher than the national average. The median age in Clayton is 39 which is approximately 2% lower than the New Jersey average of 40. In Clayton, 54% of the population over 15 years of age are married, 94% speak English and 3% speak Spanish. 69% of Clayton residents were born in New Jersey, 26% were born out of state, 2% were born outside of the United States and 3% were foreign born.