The lottery raised its jackpot estimate hours before Wednesday night's drawing and has raised it twice since Saturday's drawing by a total of about $105 million.
No one has won the Powerball jackpot for more than two months, so the prize has been growing gradually from its $40 million starting point.
It's been nearly a year since a Powerball prize topped $400 million. Officials said the jackpot will cash out to $337.8 million, either over a 29-year payment period or a lump sum payment.
Powerball is sold in 44 states as well as Washington, D.C., the U.S. Virgin Islands and Puerto Rico.
The chance of winning a Powerball jackpot is about 1 in 175 million.
The next drawing will be on Feb. 11 at 10:59 p.m. Eastern time. Powerball tickets are $2 each.