Kidney beans

One US cup of kidney beans weighs 184 grams (6.5 ounces). Going the other way, 100 grams is about 0.54 cups.

Also called red kidney beans, dark red kidney beans, light red kidney beans, dried kidney beans, dry kidney beans, rajma.

Dried beans, lentils and peas compared: cup weights side by side, the source behind each, and why they differ.

A cup of dry red kidney beans weighs 184 g (6.5 oz). USDA and the USDA Food Buying Guide agree within 1.4%, so this entry publishes USDA's figure. Confidence is medium because both are USDA sources.

Kidney beans are a large, kidney-shaped variety of the common bean (Phaseolus vulgaris), sold as dark red and light red. They are the bean of chili con carne and of rajma in North Indian cooking. Raw kidney beans contain a lectin, phytohaemagglutinin, that thorough boiling destroys, which is why dried kidney beans are soaked and then boiled hard rather than slow-cooked from raw at low heat.

USDA SR Legacy "Beans, kidney, red, mature seeds, raw" (FDC 173744) gives 1 cup = 184 g at 11.8% water. USDA's "all types" record (FDC 175193) and its royal red record print the same 184 g, so they are one figure and are not counted three times. The USDA Food Buying Guide, a separate USDA program that measures yields for school kitchens, gives 1 lb of dry kidney beans as about 2 1/2 cups, 181 g a cup.

Labels add nothing measured. Camellia prints its 1 lb bag of red kidney beans as "App. 1/4 cup (51g)" with about 9 servings. 51 g is a ninth of a pound, and Camellia prints the same quarter-cup weight on its black beans, pintos and lentils, so it divides the bag rather than weighs a quarter cup; it is kept without a figure. Store brands such as Kroger print 35 g per quarter cup on all their dry beans for the same kind of reason.

The physical check: kidney beans are among the largest dry beans, and big seeds pack less tightly in a container as small as a measuring cup, because the walls leave gaps that small seeds would fill. That is why a cup of kidney beans weighs less than a cup of small navy beans (208 g) or black beans (194 g), all three the same species, and about the same as Great Northern beans (183 g), which are similar in size. At 184 g a cup is 0.78 g/mL, the bottom of the 0.78 to 0.83 g/mL that Paixão and colleagues (2020) measured in bulk for a medium-sized carioca-type bean, as a bigger seed should be.

Cooked: USDA's boiled red kidney bean record (FDC 175194) weighs a cup at 177 g, 67% water. That is a single source, so it is given here rather than published as a second state. The Bean Institute counts 1 cup of dry beans as about 3 cups cooked and drained, so a cup of dry kidney beans makes roughly three cups of cooked ones.

Practical guidance: use 184 g per cup of dry kidney beans, 92 g per half cup; a pound holds about 2 1/2 cups. Use about 177 g per cup of cooked, drained beans. Soak dried kidney beans, drain them, and boil them hard before simmering until tender. Canned kidney beans are already cooked and only need heating.