If we haven’t yet convinced you that weight is the best way to measure flour, here’s one more argument. While testing the recipes for cookies, we noticed that equal volumes of different brands of flour don’t weigh the same. For example, 1 cup of Gold Medal unbleached all-purpose flour consistently weighed about 1/2 oz. less than 1 cup of King Arthur unbleached all-purpose flour.
To make up the difference, we needed about 2 Tbs. more Gold Medal flour. To make matters worse, the flour weights varied depending on which measuring cup we used. One particular manufacturer’s cup gave us a 4-oz. cup of Gold Medal flour, while another manufacturer’s cup of the same flour weighed in at 4-1/2 oz. These discrepancies are enough to frustrate even the most patient of cooks, and that’s why we always use a scale.