“Beans” covers a large family rather than one standardized food. Black beans, kidney beans, pinto beans, and white beans differ in fiber, minerals, and water content. The most useful approach is therefore to use representative ranges and named examples, not one universal number.
What cooked beans typically provide
| Example, per 100 g cooked | Calories | Protein | Fiber | Iron |
|---|---|---|---|---|
| Kidney beans | ~127 | ~8.7 g | ~6.4 g | ~2.9 mg |
| Black beans | ~130 | ~8.9 g | ~8–9 g | ~2 mg |
| White beans | ~130–140 | ~8–10 g | ~6–10 g | varies |
The broad pattern is consistent: a 200 g serving commonly supplies roughly 17–20 g protein plus a substantial amount of fiber.
Variety changes the number, not the basic role of the food
A difference between 8.7 and 9.5 g protein per 100 g exists, but it becomes only 1.6 g across a 200 g serving. Flavor, texture, price, digestion, and the dish you are cooking are often more useful ways to choose among varieties.
Fiber is one of the strongest reasons beans stand out
Many cooked beans provide roughly 6–9 g fiber per 100 g. A 200 g portion therefore lands around 12–18 g fiber. That is a major contrast with meat, fish, eggs, or oils, which provide 0 g fiber.
Moving abruptly from almost no beans to one or two servings a day can add roughly 12–18 g fiber at once and increase gas in some people. Raising intake gradually can be more comfortable.
They contribute iron, but absorption matters
Cooked kidney beans can provide about 2.9 mg iron per 100 g, or roughly 5.8 mg in 200 g. This is nonheme iron. Vitamin C-rich foods eaten in the same meal can improve its absorption.
Dry, cooked, and canned beans are different comparison states
Dry beans often exceed 20 g protein per 100 g because they contain little water. Once cooked, their weight rises substantially as they absorb water, bringing protein concentration down toward 8–10 g per 100 g.
Canned beans are already hydrated. Compare them with cooked beans using drained values when possible. Sodium can range from very low in no-salt-added products to several hundred milligrams per serving in salted products, so the label matters.
What about all the carbohydrate?
Cooked beans commonly contain around 20–25 g total carbohydrate per 100 g, but that figure includes fiber and starch. It is not equivalent to 20–25 g of free sugar and should not be interpreted as if all carbohydrate behaves identically.
The useful takeaway
Beans are a consistent source of plant protein and fiber, with moderate differences among varieties. The biggest comparison error is usually not choosing the “wrong” bean—it is comparing 100 g dry with 100 g cooked and treating the two values as if they describe the same amount of food.
In a real meal, roughly 7–9 ounces of cooked beans can serve as the protein base rather than merely a side dish. Pairing them with rice, corn, whole-grain bread, or another grain adds energy and a different amino-acid pattern, while peppers, tomatoes, citrus, or other vitamin C-rich foods support nonheme iron absorption. The practical nutrition of beans is therefore easier to understand at plate level than as an isolated number in a database.
Soaking and cooking also influence how comfortable beans feel to eat more than tiny protein differences among varieties. Discarding soaking water, cooking until fully tender, and increasing bean intake gradually can help some people adjust to the extra fermentable carbohydrate and fiber. With canned beans, rinsing under running water can reduce some surface sodium while leaving most protein and fiber intact.
Canned beans are especially useful when convenience determines whether legumes make it onto the plate at all. Dry beans offer more control over seasoning, texture, and batch size, but both formats can support the same basic dietary role. Compare ready-to-eat portions, choose the variety that fits the recipe, and focus on the feature they share: a relatively rare combination of meaningful plant protein, substantial fiber, and minerals in the same food.
Sources
- USDA FoodData Central — Food composition per 100 g and variation by food form, preparation, and product.
- NIH Office of Dietary Supplements — Iron — Nonheme iron and dietary factors that affect absorption.