Cassava flour

One US cup of cassava flour weighs between 120 and 140 grams (4.2 to 4.9 ounces), 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.

TL;DR: Cassava flour ranges 120-140 g/cup across brands, with the practical middle at 128 g/cup, but the critical baker distinction is between cassava flour (whole ground root, structure-building) and tapioca starch (extracted starch only, thickening and chewiness). Same plant, completely different behavior.

Cassava flour is the whole cassava root (Manihot esculenta, also called yuca) peeled, dried, and finely ground into a tan powder. Its rise to prominence as a gluten-free, grain-free, and paleo baking flour started around 2014 when Otto's Naturals launched the first widely-available branded cassava flour in the US market. Bakers use it for grain-free breads, tortillas, pizza crusts, cookies, muffins, and pancakes, often as a 1:1 substitute for wheat flour in simpler recipes (though yeasted breads generally require a starch blend for proper rise).

Density spans 120-140 g/cup depending on brand grind fineness. Independent verification by the Power Hungry baking blog compared five brands: two labeled 30g per 1/4 cup, two labeled 32g per 1/4 cup, one labeled 35g per 1/4 cup. That works out to a 120-140 g/cup range across the retail cassava flour market, a 17% spread that exceeds typical flour tolerances. Individual brand figures: Bob's Red Mill 140 g/cup (35g per 1/4 cup, coarser grind), Otto's Naturals 128 g/cup (32g per 1/4 cup, the dominant premium brand and most-referenced in recipes), Terrasoul Superfoods 120 g/cup (30g per 1/4 cup), Pereg 120 g/cup, Anthony's roughly 124 g/cup. King Arthur's Ingredient Weight Chart does not list cassava flour, leaving conversions unstandardized across recipe sources.

The critical distinction is that cassava flour is not tapioca starch. Both come from the same cassava root, but they are physically and functionally different products. Cassava flour (this entry, 120-140 g/cup) is the whole peeled root, dried, and ground. It includes fiber, protein, and root solids, has a tan color, and mild nutty flavor. Its packing density is similar to wheat flour, and it behaves as a structure-building flour that can substitute close to 1:1 for wheat flour in many quick breads and simple baked goods. Tapioca starch (existing entry, 113 g/cup) is only the extracted starch from cassava root, with fiber and root solids removed. It is white, has no flavor, and lower density (pure starch granules). It behaves as a thickener and chewiness-adder like cornstarch or arrowroot and never substitutes for cassava flour or wheat flour on its own.

The confusion is worsened by inconsistent labeling. Many US brands sell tapioca starch as tapioca flour, which is technically correct but leads home bakers to grab tapioca starch when a recipe calls for cassava flour. Brazilian and Latin American brands sometimes go further, calling cassava flour tapioca flour as well. Two products called tapioca flour, the extracted starch and the whole root, can have wildly different behaviors in the same recipe.

Physical density confirms the distinction: cassava flour at 120-140 g/cup packs similarly to wheat flour (120 g/cup) because both contain fiber and non-starch solids. Tapioca starch at 113 g/cup is lower because pure starch granules pack tighter but weigh less per volume than fiber-containing flour.

Practical baker recommendation: if a recipe calls for cassava flour, buy a package labeled cassava flour specifically, not tapioca flour (which will be pure starch and behave differently). Otto's Naturals is the most-referenced brand in gluten-free and paleo recipe development, so recipes that don't specify a brand were likely tested with Otto's at 128 g/cup. If using Bob's Red Mill (140 g/cup, coarser grind), consider reducing the volume slightly or increasing liquid to compensate for the higher mass per cup. Weigh by scale for any recipe that requires precision.