What are the chances of winning the 'must-win' Lotto jackpot?

Given the likely increase in the number of people buying a Lotto ticket for this draw, the chance of it being won by someone matching five numbers plus the bonus is 'almost certain'.

It’s been more than 60 draws since the Irish Lotto was won, but someone is definitely going to win Saturday’s €19.06m jackpot after the National Lottery received regulatory approval to hold the “must-win” draw.

So, if as has happened for every lottery draw since June, no ticket holder matches the first six numbers in the draw, then it will revert to the next highest prize tier – five numbers and the bonus, and so on until a winner is found. 

The odds are still very much not in the punter’s favour when it comes to the chances of scooping the jackpot on Saturday night but they’re still much better than they were before, according to mathematician Dr Michael Cronin, who lectures at University College Cork.

Whereas the odds of matching the first six were in the region of 10.7m to one, now it is roughly 1.8m to one of matching five numbers plus the bonus – which is actually similar to the odds of winning the Lotto when it was originally launched in 1987.

“Your odds have reduced by a factor of six,” he said. 

If someone tells you that your chances are six times better – six times is great but it’s of a chance that was very small in the first place.” 

The main €19m prize has been capped since the beginning of October and Dr Cronin said the chances of the lottery not being won for so long not as unlikely as it may seem.

He said: “By my calculations, under a 47-ball match-six game and there’s been around 663 draws since it was introduced [in 2015], the chance of a barren spell of this length is around 32/1 or 33/1. So that’s a big difference.” 

He said a 33/1 chance is likely to occur over time when an event takes place as frequently as the Lotto draw does, despite how improbable it may seem.

So, then, let’s break down people’s chances of winning Saturday night’s must-win draw.

The mathematician said under normal circumstances, the chances of matching the first six numbers to win the regular jackpot is about 10.7m to one.

As every Lotto ticket must have at least two lines on it, that means every ticket holder has at least a 5.3m to one chance to win the lotto.

If as has happened for every lottery draw since June, no ticket holder matches the first six numbers in the draw, then it will revert to the next highest prize tier – five numbers and the bonus, and so on until a winner is found.

But, as the winner could be the person who matches five numbers plus the bonus, that does shorten the odds considerably.

“With two lines, your odds are 900,000/1,” Dr Cronin said. 

“What that’s similar to is back when we had the original 36-number game [when lottery launched in 1987].” 

The mathematician stressed these betters odds are “absolutely nothing to get carried away with”, given the odds are still so high.

He added that, over the past 37 draws, no one matched five plus the bonus on 41% of these draws.

But, given the likely increase in the number of people buying a Lotto ticket for this draw, the chance of it being won by someone matching five numbers plus the bonus is “almost certain”.

He said if those who match five plus the bonus win the jackpot, it’s not unlikely there could be several winners who will share the €19m price.

Similarly, the chances of someone actually winning the Lotto outright – by matching the first six numbers – will actually be higher tonight given the increase in ticket sales expected.

“It would be so ironic if that were to happen,” Dr Cronin added.