Why tonight's Lotto jackpot will be harder to win

Powerball is getting its biggest overhaul in nearly two decades today, with the first draw under the revamped format set to take place.

From tonight, the number of Powerballs increases from 10 to 14, both the minimum and maximum jackpots are rising, and a new prize division is being introduced.

Lotto says the changes will mean "bigger prizes, bigger jackpots and more chances to win", though winning the big one is now even less likely.

Adding four more Powerball numbers jumps the odds of winning Division 1 from one in 38.4 million to one in 53.7 million.

University of Auckland mathematician Melissa Tacy said the change has a much bigger impact than people might expect.

"The way that we count out the number of different draws is multiplicative," she said.

"So even though it's only four more, you're multiplying that by an awfully large number already. When you take a really large number and even multiply it by something small, you get a really, really big change."

To put the new odds into perspective, Tacy said winning was previously roughly as unlikely as finding one specific person among seven copies of New Zealand's population. After the changes, it will be more like trying to find one person among 10 copies of the country.

While the top prize is harder to win, it's also worth more. The starting jackpot rises from $4 million to $5 million and the maximum jackpot climbs from $50 million to $60 million.

Lotto NZ said it expected around 9000 fewer winners each week across Divisions 1 to 7, though a brand-new Division 8 was designed to offset that. But at a fixed $12 prize to players who match fewer numbers it isn't going to make anyone rich.

"They're more likely to win smaller prizes more often," Tacy said

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Lotto says the changes were meant to keep Powerball "fresh and exciting" while continuing to fund community causes.

Watch tonight's draw live at 8pm on TVNZ 1 and TVNZ+