Bulk
Source Player Core pg. 25
Your character’s maximum Bulk determines how much weight they can comfortably carry. If they’re carrying a total amount of Bulk that exceeds 5 plus their Strength modifier, they are encumbered. A character can’t carry a total amount of Bulk that exceeds 10 plus their Strength modifier. The Bulk your character is carrying equals the sum of all of their items; keep in mind that 10 light items make up 1 Bulk. You can find out more about Bulk in Chapter 6.