How do you tell what PSU you need?

Haedphone

Honorable
Jun 9, 2013
4
0
10,510
I've often wondered how do you actually discern what PSU you require for your build?

*Yes i'm a bit of an "experienced" novice ^_^*

I'm not going to list any components as this is more of a rule of thumb question...

Do you simply look at what watt components draw, their total amount being additive which will therefore be indicative of what PSU you require / would want for head room in the future and if so where would one find that information or do you gauge something else?

I've always just took peoples suggestions and never really looked into it myself and when I did I could never find anything other than peoples postulations... any help would be appreciated !