Bread flour

One US cup of bread flour weighs between 120 and 137 grams, depending on how the cup is filled and which source measured it. That range is the answer; a single number would not be. Every figure behind it is below, with the method each source used.

Also called strong flour, high-protein flour, hard wheat flour, artisan bread flour.

Two sources 13.2% apart, over the 10% tolerance for the milled category, so this entry publishes a range rather than a figure. The disagreement is important because it reflects a genuine physical difference that most cup-to-gram converters obscure. USDA FDC 168896 (Wheat flour, white, bread, enriched) publishes a cup at 137 g (0.5791 g/ml).

This figure is a bench measurement of standard commercial bread flour, and it sits materially higher than USDA's figure for all-purpose flour, which the flour entry documents at 125 g per cup. King Arthur's Ingredient Weight Chart lists their Bread Flour at 120 g per cup (0.5072 g/ml), the same figure they publish for their Artisan Bread Flour, Gluten-Free Bread Flour and All-Purpose Flour. Their chart uses one weight for all standard flours regardless of type.

Bread flour is genuinely denser than all-purpose flour for two related reasons. It is milled from hard wheat rather than the blend of hard and soft wheats used for all-purpose flour, and hard wheat has a harder, denser endosperm that produces slightly denser milled particles. Its protein content is higher (typically 12 to 14 percent versus 10 to 12 percent for all-purpose), and wheat protein and wheat starch have similar densities in isolation but pack differently when milled together, with the higher-protein flour compacting slightly more efficiently in a cup.

The 14 percent gap between USDA and King Arthur is consistent with these physical differences plus the ordinary measuring-method variance for a milled powder. Most published converters use figures near 120 to 125 g per cup for bread flour, inheriting the King Arthur simplification. This is convenient for recipe adaptation but underestimates the actual weight of bread flour by roughly 10 to 15 percent when measured by dip-and-sweep from a settled bag, which is how USDA appears to have measured it.

For bread baking specifically, where hydration ratios are the whole game, the difference between 120 and 137 g per cup is the difference between an underhydrated dough that resists shaping and one that ferments and rises correctly. The practical recommendation implicit in the range published here is to weigh bread flour rather than measure it by volume; a 500 g flour weight for a standard boule is unambiguous, and 4 cups of bread flour measured by dip-and-sweep can range from 480 to 548 g between sources. Artisan bread flour, high-gluten flour, and pizza flour are related products with similar or slightly higher protein content and comparable density.

King Arthur's Artisan Bread Flour (11.7 percent protein) sits at their standard 120 g per cup on the chart. High-gluten flour (14 to 15 percent protein) is typically 5 to 10 percent denser again but no bench measurement was found from a source that names its method. Italian tipo 00 pizza flour is a soft wheat flour milled extremely fine, closer to cake flour than bread flour in density, and is a distinct product.

Vital wheat gluten (approximately 75 percent protein) is not a flour but a concentrated protein extract; USDA lists it separately at FDC 168911. FDA identity standards under 21 CFR 137.155 specify bread flour must have minimum protein content and be enriched with specific nutrients, but do not specify physical density. Codex Alimentarius CXS 152-1985 for wheat flour covers moisture, ash and particle size but not bulk density.

Two sources only, and the range is published because no third source arbitrates between USDA's bench measurement and King Arthur's category-standard figure. The range 120 to 137 g per cup is the honest answer for a home baker who cannot tell which of the two better reflects the specific flour brand on their shelf.