Wisconsin counts voter turnout as a percentage of the entire voting-age population, not just a percentage of registered voters. Also, the state allows same-day voter registration, which changes the number of registered voters.
An online article questioning 2020 results in a state that went for Joe Biden over Donald Trump claimed Wisconsin had an 89% voter turnout in 2020 -- "an impossible number that still can't be explained," according to the article.
The article falsely determined that since 3.2 million people voted out of 3.6 million registered voters, that is an 89% voter turnout.
But the Wisconsin Elections Commission reported just under 3.3 million actual voters in a voting-age population estimated at just over 4.5 million for a turnout rate of slightly less than 73%, not 89%.
The three previous presidential races had similar voter turnout rates in Wisconsin, ranging from just over 70% in 2012 to just over 67% in 2016.