Potato starch

One US cup of potato starch weighs between 152 and 193 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 raw potato starch, gluten-free potato starch, unmodified potato starch, kartoffelmehl.

Two authoritative sources disagree by 27%, well over the 10% milled tolerance. King Arthur's Ingredient Weight Chart publishes 1 cup at 152 g, implying a density of 0.6425 g/mL. USDA Branded Foods records for Bob's Red Mill Potato Starch (UPC 039978025258) publish 203 g per metric cup, which converts to approximately 193 g per US customary cup at a density of 0.8158 g/mL. Both are authoritative sources, and the gap between them is real, driven by differences in grind fineness and packing method between the products the two sources measured.

Potato starch is a remarkably dense powder for its category. The upper-end density of 0.8158 g/mL approaches the density of crystalline sugar (approximately 0.85 g/mL) despite potato starch being a fine powder rather than a granular crystal. This reflects the physical composition: potato starch is near-pure carbohydrate with almost no fiber, protein or air-trapping cellular structure. The starch granules pack tightly against each other when scooped, leaving less air space than flours that contain fiber and germ material. King Arthur's lower figure of 152 g per cup likely reflects a lightly spooned fill; the higher figure reflects a tapped or shaken fill closer to the product's true bulk density.

Home bakers using potato starch in gluten-free blends, as a thickener for sauces and gravies, or in Passover baking (where it substitutes for wheat flour in matzo recipes) should weigh rather than measure by volume. A 40 g error over a cup (the difference between 152 g and 193 g) significantly changes thickening power in sauces and hydration balance in doughs.

Critical disambiguation: potato starch is not the same product as potato flour. Potato starch is the pure carbohydrate extracted from potatoes by washing and drying, containing no fiber, protein or minerals of note. Potato flour is dehydrated whole potato (including skin in some products) ground into a powder, containing all the fiber, protein and moisture-absorbing components of the original potato. Potato flour typically weighs around 160-180 g per cup and has completely different baking behavior: it absorbs approximately four times its weight in water and imparts a distinct potato flavor. Potato flour is a separate product not covered by this entry.

Potato starch sits in the milled category alongside all other fine powdered starches (cornstarch, tapioca starch, arrowroot). The 10% category tolerance applies here, and the observed 27% gap between authoritative sources clearly exceeds it, hence the range publish. The gap is larger than most milled ingredients on this site because potato starch has an unusually wide range of packing behaviors: the fine granules can settle very tightly under vibration but scoop loosely when disturbed.

Related products: cornstarch is covered by a separate entry with its own range (112-128 g per cup). Tapioca starch, arrowroot starch and rice starch are distinct products not yet fully covered on this site. Sweet potato starch is another distinct product from a related but different crop.

No standards body publishes a bulk density for potato starch. Codex Alimentarius standards for edible starches (CXS 176-1989 for starches in general) cover purity, moisture content, ash content and sulfur dioxide limits rather than physical density. Two authoritative sources with real product variation, so this entry is held at low confidence and range published until either a third authoritative source resolves the split or USDA SR Legacy adds a cup-portion reference for pure potato starch.