1 in 18 septillion.
Lottery legend Joan Ginther supposedly defied such stupefying odds to win four multimillion-dollar lottery prizes, the Associated Press reported after she won $10 million in 2010.
Not so fast.
Those aren't the odds of such an event ever happening. Those are the odds for this particular individual if she bought exactly four tickets.
It makes a huge difference.
The chance of you winning Powerball with a single ticket is 1 in 175 million.
So the chance of one of those people winning a second time is roughly 200 out 175 million (if each bought only one ticket), or better than 1 in a million.
That's a lot better than multiplying 1 in 175 million by itself and getting 1 in 30.6 quadrillion.
Furthermore, it's not even clear Ginther's first win should count. Word around town was that her father bought the winning ticket and let her claim it, as explained in Part 1 of this series.
Still, Ginther is an extreme case, since she went on to win $3 million playing Millions & Millions in 2008 and $10 million playing $140,000,000 Extreme Payout in 2010, apparently defying odds around 1 in a million each time.
Actually, her real odds were far less lousy.
First, the odds change during scratch-off games, depending on total top prizes left as sales relentlessly continue, and Ginther often played when they were more favorable, often more like 1 in 600,000, perhaps even as low as 1 in 200,000.
She also played at least eight games, further improving her chances of winning top prizes.
Most importantly, she apparently bought thousands of tickets, even tens of thousands, according to expert analysis of the many prizes she claimed.
If estimates of Ginther's extreme ticket-buying habits are accurate, the odds of her winning three major scratch-off prizes -- not just one -- may have been as low as 1 in 1,300, according to a lottery industry analyst.
More like choosing the right grain of sand from a teaspoonful, rather than from all the beaches on Earth.
A little tougher than hitting a Pick 3.