A 100-gram serving of cooked red kidney beans contains about 127 calories. That’s roughly half a cup, making red beans one of the more calorie-efficient ways to get a significant amount of protein and fiber in a single food.
Calories by Serving Size
Most people don’t weigh their beans on a scale, so here’s how the numbers break down in practical terms. A half-cup (90 grams) of cooked red kidney beans comes to about 113 calories. A full cup lands around 225 calories. These numbers assume plain cooked beans with no added fat, salt, or seasoning.
For context, that cup of red beans delivers nearly 16 grams of protein and close to 13 grams of fiber, which is over 40% of the daily recommended fiber intake. Very few foods pack that much nutrition into 225 calories. The fat content is negligible at about 1 gram per cup.
Canned vs. Home-Cooked Beans
Canned red beans are slightly higher in calories than home-cooked ones. A 180-gram serving (just under a cup) of canned, drained red beans has about 243 calories compared to 227 for the same amount cooked from dried. The difference is small, but canned beans also carry more sodium: roughly 560 milligrams per serving versus 396 milligrams for home-cooked. Rinsing canned beans under running water before eating can wash away a good portion of that extra sodium.
Full Macronutrient Breakdown
Per 100 grams of boiled red kidney beans:
- Calories: 127
- Protein: 8.7 grams
- Carbohydrates: 22.8 grams
- Fiber: 6.4 grams
- Fat: 0.5 grams
- Sugar: 0.3 grams
- Water: 67%
The carbohydrate count looks high at first glance, but more than a quarter of those carbs come from fiber, which your body doesn’t absorb as energy. The actual digestible carbohydrate load is lower than the label suggests.
Red Kidney Beans vs. Other Red Bean Varieties
The term “red beans” can refer to several different legumes depending on where you live. Red kidney beans, small red beans (common in Louisiana-style red beans and rice), and adzuki beans (popular in East Asian cooking) are all called “red beans” in different cuisines. Their calorie counts are similar when compared dry: adzuki beans have about 329 calories per 100 grams dried, while red kidney beans come in at 337. Once cooked, both land in the same general range of 125 to 130 calories per 100 grams, since they absorb roughly the same amount of water.
Key Micronutrients
Red beans are an unusually rich source of three nutrients many people fall short on. One cup of cooked red kidney beans provides about 658 milligrams of potassium (roughly 14% of the daily target), 3.2 milligrams of iron (about 18% of the daily value for men, less for premenopausal women), and 131 micrograms of folate (about 33% of the daily value). Folate is especially important during pregnancy for fetal development, which is one reason beans are a staple recommendation in prenatal nutrition.
Why Beans May Be Lower-Calorie Than They Appear
Cooked red beans contain about 4 to 5% resistant starch by dry weight. Resistant starch behaves differently from regular starch. Instead of being broken down and absorbed in your small intestine, it passes through to your large intestine mostly intact, where gut bacteria ferment it. This means your body extracts fewer usable calories from beans than the nutrition label implies. Resistant starch also slows the release of glucose into your bloodstream, which helps keep blood sugar more stable after a meal. This is one reason beans have a low glycemic index despite being a high-carbohydrate food.
Cooking Dried Red Beans Safely
Raw red kidney beans contain a natural toxin called lectin that can cause severe nausea, vomiting, and diarrhea if the beans aren’t cooked properly. The fix is simple but specific: soak dried beans for at least 12 hours, then boil them vigorously in fresh water at a full rolling boil for at least 10 minutes. After that initial boil, you can reduce the heat and simmer until tender.
Slow cookers are a concern here because they often don’t reach a high enough temperature. Research has shown that cooking beans at 85°C (185°F) for an hour still leaves the toxin active. A slow cooker on its low setting typically stays below that threshold. If you want to use a slow cooker, boil the beans on the stovetop first, then transfer them. This applies specifically to kidney beans, which have much higher lectin levels than most other legumes.