Stats professor reveals your chance of winning $120m Powerball prize

A statistics professor has crunched the numbers on your chances of winning the $120 million in the Powerball draw tomorrow night.

"We have 35 possible numbers, we choose seven of those ... now to account for the Powerball, there are 20 possibilities there," Jake Olivier from the University of New South Wales told A Current Affair.

"This is a factorial, so seven factorial, times seven times, six times, five times, four times, three times, two times, one, that's to account for all the unique ways that these numbers can arise."

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The professor said he believes the chance of winning the big prize "roughly works out to be (one in) 134 million".

The Lott spokesperson Matt Hart said they "expect up to half of all adult Australians to have an entry in this $120 million draw".

Mr Hart said his job entails calling lucky Powerball winners.

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"That news is either met with complete silence and a stunned response or some colourful expletives," Mr Hart said.

Mr Hart said in his position he often gets to find out what people will spend their winnings on too.

"I think one of the most unusual things was we did have a division one winner who wanted to buy a new washing machine," Mr Hart revealed.