The survey, conducted by Morning Consult, indicated one in five adults will place a bet on the tournament. Over 11,000 adults were interviewed online between 1 and 7 March.
The main findings of the survey include: 47 million American adults will wager $8.5bn on March Madness, while nearly 18 million people will wager $3.9bn at a sportsbook, online, with a bookie or with a friend.
However, 2.4 million will still bet illegally with an offshore bookmaker, according to the extrapolated data.
Bill Miller, AGA President and CEO, said: "Unlike any other sporting event in the country, March Madness attracts millions who fill out brackets, make casual bets with friends or wager at a legal sportsbook, which Americans can now do more than ever before.
"These results indicate there’s still work to do to eradicate the vast illegal sports betting market in this country, and we’re committed to ensuring sound policies are in place to protect consumers."
