Measuring accurately can make or break a recipe, especially when it comes to baking. When you need to rely on precise measurements, nothing beats a scale. Especially when it comes to flour. Flour amounts can vary dramatically by volume depending on how you measure each cup: whether you scoop and level, lightly spoon, or sift it into the dry measure.
Even using the same method, weight can vary from cup to cup. We ran an experiment in the Test Kitchen three years ago where everyone measured a cup of flour by lightly spooning it into the dry measure. Each person came up with a different weight, the results varying from 3 1/2 ounces per cup to more than 5 ounces per cup.