

I have an arena that contains around 15 cages filled with animals, and that settlement gets attacked most times that I visit, and is constantly being attacked when I am away from it, despite having a defense rating of over 400 and a resource production a little over 100.

One thing that will almost ensure attacks on settlements, if you have the Wasteland Workshop DLC, is having occupied animal cages at a settlement. However I'm not sure of the algorithm to calculate how much more likely it is that they will be attacked. My settlements with a defense rating higher than or equal to the combined resource production have definitely been attacked before. So the chance of attack is always at least 2% per day (unless it's already been attacked in the last week or there are no settlers), but it's not hard to get it that low. Settlement with 200 food + water, 0 defense, and 2 settlers = 2 + 20 - 0 - 1 = 21% Settlement with 50 food + water, 10 defense, and 10 settlers = 2 + 5 - 10 - 5 = -8 => 2% (min value) Thanks to /u/matzman666 for pointing that out.)ĭefense and population subtract from that: defense + (population / 2) % (Note that food and water items in your workshop inventory count towards these totals. Resources add to that: (food + water) / 10 % There are apparently some quests and triggers (I don't have a list of all these triggers) that can force an attack, which will ignore everything I'm about to tell you.Ī Settlement will only be attacked if it has at least one population.Ī Settlement will not be attacked more than once every seven days.Įvery day, there's a chance for your Settlement to be attacked:

I've copied over the formula for raid chance and associated notes, with some formatting improvements: The thread is 4 months old, so it's possible this has been tweaked in a patch since then. There's a reddit thread where this is discussed, including a formula.
