Originally Posted by Toots
OK - one more question for you sage scale users : what if the recipe calls for 3 cups of flour and I want to measure it on my scale - how would I convert it? just do the reverse of the advice above (5 oz per measured cup) to come up with the correct weight?
Not if you want the right answer!
The unit weight per volume can be different between different flours. For example - if you look at the nutrition information on the side of the flour bag you'll see the "serving size" - which is a unit weight per volume. In the case of a bag of Pillsbury Best AP flour - 1/4 cup = 31 grams. So ... 1 cup would be 124 g = 4.37 oz/cup.
If you want to get a little more accurate, take the weight of the bag (in oz or grams) and divide by the number of servings in the bag and adjust for 1 cup ... in this case, 32 oz / 29 (1/4 cup servings) x 4 (to get 1 cup) = 4.41 oz ... which is what the flour converter that Russellkhan posted a link to comes up with.
If you use an arbitrary number like 5 oz/cup - you will have 12%-14% too much flour (basically about 1/2 cup minus 4 teaspoons too much). If you're going to buy scales to measure flour you might as well get the right answer!