You’re good with numbers and logistics. How many Kingsguard would you say there have been in total since the order was founded? We’ve got around 60-70 named so far. 200? 250? This spun out of wondering whether it would be even remotely feasible for Martin to write the White Book. Seems like a staggering amount of world building, even by his standards.

HAH! I’m actually terrible with numbers, but I force myself to struggle through the math because I need to understand it. 

For a baseline estimate, I would say that, given that a generation is around 30 years and there have been 300 years of Targaryen rule, you’re probably looking at a minimum of 100 Kingsguard. Probably a little more, since the work of the Kingsguard is more dangerous than most. So I would guess between 100-200.