We are some times guided by the sizes sold in supermarkets. If you have a lot on the way, pick and use them as needed/wanted.
Remember commercial growers are out to get as much as they can for a perfect size as per EEC standards.
I prefer my fruit and veg a little smaller, tender with compact flavour and ripe when picked. Rather than big, well presented, harvested too early so they have a shelf life.
Grow your own for the freedom to choose.