While election officials are still tabulating ballots, the 126 million votes already counted means about 55% of voting age citizens cast ballots this year.
That measure of turnout is the lowest in a presidential election since 1996, when 53.5% of voting-age citizens turned out.
As election officials go through outstanding ballots -- such as provisional ballots and those with write-ins -- the turnout figures will change.
But it would take another 18.7 million votes to reach the high point for turnout of 2008, when nearly 64% of voting age citizens cast a ballot.
Early results in some of the key states that propelled President-elect Donald Trump to his win reveal that more voters cast ballots this year than in 2012, even though overall turnout was down.
In Florida, nearly 9.4 million ballots were cast, compared to 8.5 million in 2012. Michigan saw 4.8 million compared to 4.7 million four years ago. And in North Carolina, the 4.7 million ballots this year was about 138,000 more than last cycle.
Full measures of turnout won't be clear for as long as several more weeks, when election officials in the various states finish tabulating and certify the results. The figures also do not include people of age who are ineligible to vote or have not registered.