All-purpose flour

There is no single weight for a cup of all-purpose flour, and this page does not print one. What a cup weighs depends on how the cup was filled, and the published sources measure it different ways.

Also called plain flour, AP flour, white flour.

Flour publishes no number, and that is the entry's finding rather than a gap in it. Three sources give 141.75 g, 125 g and 120 g per cup. They are not three disagreements about one quantity; they are three quantities, because each describes a different way of filling the cup.

America's Test Kitchen name dip-and-sweep and give 5 oz, arrived at by having dozens of volunteers each measure a cup and averaging the results, and they state that technique alone can produce up to a 20% difference. King Arthur's Recipe Success Guide gives 120 g and instructs the reader to spoon the flour in gently and sweep off the excess. USDA records an 'undetermined cup' at 125 g and names no method at all, so its state stays 'unspecified' under decision 21.

The spread from 0.5000 to 0.5906 g/ml is 18%, which stops the entry under rule 5 and splits it under rule 6, because two of the three sources name their own state rather than leaving it to be inferred from the figure. Splitting leaves each state with exactly one source, so all three are withheld under decisions 23 and 27 and the entry drops to low confidence. The earlier version of this entry paired USDA's 125 g with King Arthur's 120 g, called the 4% gap a difference of method and held it at medium confidence.

That was wrong in a way worth recording: the two figures sat inside the 5% limit only because the third method was missing from the file, so a method difference was passing as a measurement agreement. Adding the source that names dip-and-sweep is what exposed it. King Arthur's own measuring guide separately states that a fluffed, scooped and levelled cup holds around 120 g while a more condensed cup can hold up to 160 g.

That upper bound brackets the ATK figure rather than contradicting it, but it is the same publisher and confirms nothing independently. Note also that King Arthur's 120 g is stated for their own Unbleached All-Purpose Flour, not for all-purpose flour generally, and that they name the same technique three ways across their site: 'fluff, sprinkle and scrape' in their video, 'fluff, scoop and level' in their 2023 measuring guide, and the spoon-and-sweep wording quoted above. The method field records the wording of the page cited, not a tidied label.

To publish, each state needs two further sources that name its method and measure it. Unverified lead: Mel's Kitchen Cafe reports testing dip-and-shake at 6 oz, dip-and-sweep at 5.25 oz and spoon-and-sweep at 4 oz. A blog, but it states method and describes testing, so it must be verified at source and judged against the independence test in decision 25.

Cook's Illustrated is the same organisation as America's Test Kitchen and is not independent of it. The eatyourbooks summary reports other people's figures and is not a source.