White rice

One US cup of white rice weighs between 185 and 198 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 long-grain rice, uncooked rice, raw rice.

Two sources, both measuring uncooked long-grain white rice, 7.0% apart. USDA FDC 168877 gives a cup at 185 g, or 0.7819 g/ml, and publishes the same figure for the unenriched record at FDC 169756, so enrichment does not affect the weight. King Arthur's chart gives half a cup at 99 g, or 0.8368 g/ml.

Neither source names a method, so the gap cannot be split into states under rule 6, and neither can be preferred without a third source. The range is published instead of a figure. Rice sits awkwardly between the categories this dataset uses.

It is not a liquid, where any two measurements should agree closely, and it is not a milled powder like flour, where clumping makes wide disagreement expected. It is whole hard grains, which pour freely like crystalline sugar but are large enough relative to a cup that how they settle matters: grains bridge against each other and against the wall of the cup, and tapping or pouring from a height changes what fits. That suggests a tolerance wider than the 5% that suits liquids, but no measured evidence was found for how much wider, and setting a category tolerance to make a particular entry publish would be choosing the answer first.

Rice is therefore held at the default tolerance and publishes a range until either a third source settles the figure or someone measures how much settling actually changes. Cooked rice is a separate product rather than a state of this one. USDA gives cooked parboiled long-grain at 158 g per cup (FDC 169708), but the grains have absorbed water and roughly tripled in volume, so the two figures describe different substances in the way that butter and whipped butter do.

Brown rice is likewise not covered here; King Arthur lists it cooked only. No standards body publishes a bulk density for rice. Grain trading uses test weight, measured in pounds per bushel, which is a different quantity measured by a different apparatus and cannot serve as a source under rule 3.