The county had roughly 621,000 residents at the start of 2026, about 60,000 more than counted in the 2020 U.S. census. That amounts to an increase of about 11%. Wisconsin’s population grew by roughly 170,000 over the same period, reaching just under 6.1 million, a gain of about 3%.

Dane County accounted for more than a third of the state’s growth since the census, based on the state estimates. The figures are calculated using indicators including housing data and vehicle registrations.

Growth was especially rapid in communities surrounding Madison. DeForest and Cottage Grove each grew by more than 30% since 2020, while Verona, Windsor and Fitchburg grew by more than 20%. Waunakee, Middleton, Oregon and Sun Prairie each increased by more than 10%. Madison’s population rose about 9%, to slightly more than 300,000.

The state’s estimates are notably higher than the U.S. Census Bureau’s figures. The federal agency estimated Dane County’s population at about 590,000 last year; the state estimate at the time was about 611,000. Different methods and data sources can produce different population estimates.

The distinction matters because population counts inform public decisions. Decennial census figures help determine some federal funding and are used in drawing congressional districts, while state population estimates factor into some state funding decisions. Local planning specialists expect the Madison area to keep growing, raising ongoing questions about how communities will accommodate new residents, including through housing and infrastructure planning.