The 2015 population estimate for Chester County is 515,939. From 1930 to 1980, the County increased by approximately 190,000 people. From 1980 to 2010, it grew by just over 180,000. During that time the share of population living in boroughs and Coatesville City shifted from almost 50% to under 20%. Currently, the county population is about the same as Atlanta, GA, Kansas City, MO, and Sacramento, CA.

By 2045, the population in Chester County is projected to increase by over 146,000 for a total population of 662,000. The municipalities projected to grow by more than 4,000 new residents are largely clustered around Downingtown Borough. Other projected growth areas are the Great Valley, the Route 1 corridor, and communities bordering Montgomery County.