Tapioca starch

One US cup of tapioca starch weighs 113 grams. Going the other way, 100 grams is about 0.88 cups.

Also called tapioca flour, cassava starch, tapioca powder, tapioca starch or flour, gluten-free tapioca starch.

Tapioca starch publishes at 113 grams per cup based on King Arthur's authoritative baking figure, with a producer consensus at 120 g/cup providing a second data point 6.2% higher, well within the 10% milled tolerance. Bob's Red Mill labels tapioca flour at 4 teaspoons = 10 grams, which extrapolates to 120 g/cup, and multiple other producers (Expandex Modified Tapioca Starch, bulk-bin tapioca powder, finely-ground tapioca flour) publish 1/4 cup = 30 g, also landing at 120 g/cup. The 6.2% gap between KA's 113 and the producer cluster's 120 likely reflects differences in fill method, with KA measuring a lightly-packed cup and commercial serving-size labels reflecting typical spoon-scoop packing that lands slightly denser.

Tapioca starch and tapioca flour are two names for the exact same product: fine white powder made from the starch of the cassava root (Manihot esculenta, also called yuca or manioc). King Arthur explicitly treats the two names as synonyms on their Ingredient Weight Chart, and this entry does the same. This is different from wheat starch versus wheat flour, where the two are distinct products. In tapioca, the starch fraction is essentially the entire product because cassava root contains almost no protein, fat, or fiber to separate out. The 'flour' name persists mostly from gluten-free baking terminology and from Southeast Asian cooking, where tapioca flour has been a pantry staple for generations, while the 'starch' name predominates in commercial food manufacturing.

USDA does not publish cup portion data for tapioca starch or flour. The one USDA record for tapioca (SR Legacy 169717, 'Tapioca, pearl, dry') covers the rolled dry pearl form used in tapioca pudding and boba tea, which is a completely different product state. Pearls are made by moistening tapioca starch and rolling or extruding it into small spheres, then drying the spheres. The finished pearls are dense and pack at 152 g/cup, roughly 35% heavier than the loose starch powder form. This entry documents the powder state only, and bakers looking for the pearl weight should consult USDA directly.

Compared to other starches and gluten-free flours on the site, tapioca starch at 113-120 g/cup sits in the middle of the density band. Cornstarch is similar (KA publishes 120 g/cup, same producer-consensus figure and same fine-powder physics). Potato starch is denser (roughly 160 g/cup because the starch granules are larger and pack more tightly). Almond flour is much denser at 96 g/cup for the blanched version because it contains fat and protein rather than being pure carbohydrate. All-purpose wheat flour at 120 g/cup is close to tapioca in density because both are fine powders with similar granule size distributions, though they differ dramatically in baking behavior.

Category assignment is milled, matching all other flours and starches on the site. Tapioca starch is a fine dry powder that packs as a milled particulate, not as small crystalline solids like sugars or salts. The sugar category is reserved for granulated sugars, salts, chocolate chips, and small dried fruits.

Confidence is medium. King Arthur provides one authoritative figure, and multiple independent producer sources cluster at 120 g/cup, giving cross-validation across brands and packaging conventions. The main source of remaining variance is fill method: a scooped cup packs slightly denser than a spooned-and-leveled cup, and different bakers measure differently. Bakers using recipes that specify a particular brand should trust that recipe's implicit weight; when in doubt, weigh the starch rather than trusting cup measurements.