Derby, CO has a population of 8,930 and is the 4,297th largest city in the United States. The population density is 5,097 per sq mi which is 10138% higher than the Colorado average and 5526% higher than the national average. The median age in Derby is 29 which is approximately 20% lower than the Colorado average of 36. In Derby, 51% of the population over 15 years of age are married, 55% speak English and 45% speak Spanish. 60% of Derby residents were born in Colorado, 16% were born out of state, 1% were born outside of the United States and 23% were foreign born.