I've got two settlements on the go that I'm paying attention to – Sanctuary and the Starlight Drive In. Both of these settlements have radio towers and beds and all resources in the green however they appear to have stopped growing at 10 people in each settlement even though happiness is above 80 and I've got 15+ beds at each location.
What is the maximum number of people that will join a settlement?
Best Answer
Temporary charisma buffs will make it possible to get a lot more settlers according to this steam thread
This reddit thread also confirms going over 22 but reverting to normal when going back :
The number is 10 + 1 per charisma point as written here:
Seems the defense's value needs to be higher for a safe settlement, as per the comment from DCShannon :
So make sure you have enough water, food and defense with at least 1 charisma to get up to 11 and more.
So the max should be 21 as it is possible to get a SPECIAL over 10, with charisma at 11, that would make possible to have 21 settlers with the same amount of beds, food, water and defense.