Average family size

The ONS state the average family size in the UK to be 2.4. They also state that the average number of children per female to be 1.7. The breakdown of both stats is available on their website results by search both terms.

In a previous job I used to be involved in water demand forecasting. We had a fairly extensive dataset (from census data) and it varied surprisingly significantly by area. But on the whole; 2.5 people per home.

https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/articles/familiesandhouseholdsstatisticsexplained/2021-03-02

That says that a (edit: ONS) family includes a couple living together without children. Unless I'm reading it wrong.

I want the average size for families that have children (i.e. not including co habiting but childless couples).

The average family size will always be lower than the mean ultimate family size, which is a more useful tool.

Mean families aren’t nice

Ultimate or otherwise

I’m trying to work out if that is the average number of kids per female, or the average number of children for a couple that has children

kids per female would more likely covered  be ‘fertility rate’ rather than family size as ‘household’  or a ‘family’ might not have a ‘couple’ in it with or without children

Your question is quite interesting, but are you really interested in children per female?  Eg there will be a number of families where the mother has died, probably more where she is estranged and the father looks after the kids.  Do those matter to whatever analysis you are trying to do?  Are you interested across all ages, or only 0-18yr old children?  Eg, does a 19yr old student who is at home only during the holidays matter?  What about a 17 yr old in the same boat (not uncommon in Scotland).  If you are interested in the ultimate “family size” people in the U.K. get to - does including only-children less than say 5 yrs old introduce a bias to the stats?  What about looked after children (foster care etc?) or generations where young mums still live with their own parents.  How about coparenting arrangements - does a mum who has two kids 3.5 days a week = 1 kid? But if not is dad who has them the rest of the time double counted?

I'm basically interested in understanding whether as a family of 2 kids and 2 adults, whether we are above or below the average (mean) for families that have kids. If I am interpreting the ONS note correctly their definition of a family will include those families that are just two adults co-habiting and skew it downwards. Likewise if I look at fertility per female then again that will be skewed downwards by childless females.

Poly, you're making interesting points about definitions. Upon reflection I guess I want the mean number of children per female where the female has had at least one child for females under 45. Tho that's a proxy, what I really want is probably mean number of children for two person cohabiting families who are currently of child bearing age (say 20-45) and have at least one child in the UK. I doubt the later stat exists but maybe the former does?

I’m basically interested in understanding whether as a family of 2 kids and 2 adults, whether we are above or below the average (mean) for families that have kids.

It'd tricky because you also need to account for where the kids are - if you had a kid at 25, and now you're 43 and the kid is living away at university, do you count as a 'childless couple'?

So I am just interested in couples (or if that proves impossible at a push females) that have had at least one child. So in this case the child that lives away from home would be included.

I think you will find what you need (or at least a long way towards it) here:

https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/datasets/familiesandhouseholdsfamiliesandhouseholds

perhaps table 4?

You seem to be very much average.

Two is about average, plus or minus an arm or a leg or two (not that that's usually possible).

Most people have more than the average number of legs.

Ah thanks Poly, I think that's what I'm after.