Legumes create one of the most common nutrition-table contradictions: one source says lentils have 24–25 grams of protein per 100 grams, another says 9. Both can be right. One is usually dry; the other is cooked and full of absorbed water.
If the question is what actually reaches the plate, cooked and drained legumes are the fairest comparison. Seen that way, soybeans and lupini beans stand apart while lentils, chickpeas and many common beans nearly tie.
The ranking when all of them are cooked
| Legume | Protein/100 g |
|---|---|
| Mature soybeans | 18.2 g |
| Lupini beans | 15.6 g |
| Lentils | 9.0 g |
| Black/pinto beans | ~8.9 g |
| Chickpeas | 8.9 g |
| Kidney beans | ~8.7 g |
| Green peas | ~5.4 g |
Soybeans sit in a different range
Cooked mature soybeans provide about 18.2 g protein/100 g, roughly twice the 9 g in cooked lentils. A 1-cup serving around 170 g supplies about 31 g protein.
They are also higher in fat and calories: roughly 170 calories/100 g compared with 116 for cooked lentils. The extra protein comes as part of a different overall food profile, not as a free bonus.
Lupini beans are another outlier
Cooked lupini beans are around 15.6 g/100 g, well above lentils and chickpeas. In the U.S. they are often sold in brine, so sodium can be substantial; rinsing can remove some surface brine.
Lentils, chickpeas and beans are basically a cluster
These foods sit tightly around 8.7–9.0 g protein/100 g. A 1-cup serving provides roughly 18 g from lentils, 18 g from chickpeas and 15–18 g from many common beans depending on the exact type and serving weight.
When the difference is a few tenths of a gram, taste, texture, fiber, tolerance and the recipe are better reasons to choose one than the protein leaderboard.
Why dry numbers look so much higher
Dry lentils contain about 24.6 g protein/100 g compared with 9.0 g after cooking. Their water content rises from roughly 8% to around 70%.
The pot has not destroyed most of the protein. It has added a large amount of water, so the same dry matter is spread across much more total weight.
Canned beans already belong in the “cooked” comparison
Canned beans are hydrated and cooked, so their composition is much closer to cooked beans than dry beans. Brand, variety and packing liquid can shift the numbers; draining and checking the label gives the most useful product-specific comparison.
Peanuts are legumes — but nutritionally they play a different role
Peanuts are botanically legumes and contain about 25.8 g protein/100 g, higher than cooked soybeans. But they are eaten dry like nuts and contain roughly 49 g fat and more than 560 calories/100 g.
So including peanuts in a “highest-protein legumes” list is botanically correct and potentially misleading unless the dry, calorie-dense context is made clear.
What a normal serving contributes
| Legume | Serving | Protein |
|---|---|---|
| Cooked soybeans | 1 cup / ~170 g | 31 g |
| Lupini beans | 1 cup / ~166 g | ~26 g |
| Lentils | 1 cup / ~200 g | 18 g |
| Chickpeas | 1 cup / ~200 g | ~18 g |
| Black beans | 1 cup / ~172 g | ~15 g |
And legume protein arrives with fiber
One cup of cooked lentils provides about 18 g protein and roughly 15–16 g fiber. An equivalent 200 g weight of chicken breast provides more than 60 g protein but no fiber.
They are not better and worse versions of the same food; they serve different nutritional roles.
The useful takeaway
Soybeans and lupini beans are the most protein-dense cooked legumes in this group. Lentils, chickpeas and common beans are much closer together and all contribute meaningful protein in a normal serving.
Within that second group, variety is more useful than chasing a fraction of a gram.
Sources
- USDA FoodData Central — Cooked legume composition.