This article reports on the measurement and valuation of the output of the household production of childcare. This includes all care given by parents, family members, friends and focuses on the numbers of children looked after, rather than those giving the care. It is the first in a series of articles to update the full household satellite accounts (HHSA) for the UK. The methodology remains under development and any estimates reported here, or in forthcoming publications, should be considered experimental and interpreted with caution. (author abstract)