kinda missing the point here. I know that one cup is always the same size. I also agree that converting volume to gram is easy, but volume is just an inherently bad way of measuring for baking. here is why:
you can cramp one cup full of flour and it will be 250g and you can pack it lightly and it will be 210g. these variations can't be avoided, you will never fill a cup exactly the same. with a scale it's irrelevant. also, if you use different types of flour they will vary in volume, say 1 cup of type 405 will have a different weight from one cup of 510 flour, you feel me? and you definitely cannot adjust for that with your eye, or your "feeling". I don't always follow recipes, and I can do a pretty good bread or pizza dough just by eyeballing, but the best bread I make then I try really hard. and that means following a recipe to a t. yeah, with baking cookies a few grams of flour wont make a big difference, but if you make a soufflet or a brioche or a loaf of bread it's pretty important to be exact.