I'm quite relieved by this thread as other threads like this I've seen are dominated by the "family of 6, we do 3 loads a week" and it's unbelievable to me.
Family of 4 with pets (although frankly, t hey don't add THAT much to our washing) and we do:
4-5 small loads because DH has a small load of work clothes that have to be washed every day and usually separate so I exclude those as it's a weird and irritating aberration.
2-3 loads of bedding per week (our bedding is changed weekly, kids fortnightly. Kingsize for us with added double bed duvet for me, singles for the kids).
2 loads towels - bath sheets and swimming towels so take up space
3-4 loads of darks
1 load whites
The towel/bedding/darks loads will be higher on weeks I am washing all the random dog towels/mats or doing loads of coats for example, but those aren't done weekly.
And while DD does have an irritating habit of adding things to washing basket if she's so much as looked at them, overall, we're not a family of "wore for 10 minutes, MUST BE WASHED."
But I worked out once that just underwear and pjs would basically be well over one full load. it's 4x7 underpants/panties, 4x7 PJ pants or similar. PJ tops tend to be worn twice each but still 2x7 say. I wear a vest daily except in the absolute height of summer, so that's 7 vests. 4 x 7 pairs of socks. Bras are worn for more than one day (me) so let's say x3, and DD has started wearing bralettes on days she has PE or non-leotard dance days so let's say that's another 3. Then on top of that, DD does dance 3x a week, DS has extracurricular sport as often as 7 days a week. PE kits are washed weekly....
And all this before we get to the everyday wear of t-shirts, and trackies and jeans and shirts etc. Proper jumpers are washed infrequently - I do a delicates/wool cycle about once a month only - but there's still plenty!