US Cups, Grams, and Kitchen Scales
Why US cup volumes differ from metric cups and how ingredient density makes cup-to-gram charts necessary.
Two Different "Cups"
The US legal cup is 236.588 mL. Many metric recipes imply 250 mL. That 13 mL gap changes weights when you assume water density.
Density Beats Volume for Dry Ingredients
A cup of flour and a cup of sugar occupy the same volume but not the same mass. Charts like King Arthur list grams per US cup for each ingredient.
Spoon, don't scoop flour
Scooping compacts flour and can add 20%+ extra weight versus spooned and leveled cups.