usually this is set as an inheritance in percentages from the max width of the viewport, which comes through the body tag to whatever you're working on typically this is a thing you tell an element rather than asking an element

yeah i understand it, i just always think of large codebase with infinite contributors where you’re responsible for some small part of this and if someone in charge of your parents adds some padding or margin without telling you, you could just be broken unless you’ve variable encoded EVERYTHING