That's the figure put forward from research at the Post Office with many parents saving almost £90 a week thanks to their own parents.
"Significantly, 34% of those unable to rely on their own parents for support will have to take leave from work," says the Post Office.
"A further 31% claim they would need to pay for a childminder or for their child to attend a holiday club during the school summer holiday, which - depending on where you live - stretches from mid-July to the end of August."
Unsung heroes? Definitely. But what about all that free advice on how to bring up children? There's no estimate from the Post Office on that area but perhaps that sort of guidance is priceless anyway.
Even if you ignore much of it.
Many grandparents will certainly be coming to the rescue as thousands of public sector workers strike. It's also increasingly the sort of help money can't always buy easily, including tutoring, chauffeuring, special trips not to mention basic child care.