How many carbs are in black beans?
Black beans has 20.4 g of total carbs per 1/2 cup cooked (86 g) — about 12.9 g net carbs after 7.5 g of fiber. That's 23.7 g of carbs per 100 g, roughly 7% of the 275 g Daily Value.
USDA FoodData Central · cooked, boiled · FDC 173735
Carbs by portion
| Portion | Total carbs | Net carbs | Fiber | Sugar | Calories |
|---|---|---|---|---|---|
| 1/2 cup cooked (86 g) | 20.4 g | 12.9 g | 7.5 g | 0.3 g | 114 |
| 100 g | 23.7 g | 15 g | 8.7 g | 0.3 g | 132 |
| 1 oz (28 g) | 6.7 g | 4.2 g | 2.5 g | 0.1 g | 37 |
Net carbs = total carbs − fiber (the carbs that raise blood sugar, used in keto/low-carb tracking). Values computed from USDA per-100 g data (FDC 173735, SR Legacy). cooked, boiled.
Black beans look carby on paper and eat much lighter — that gap is the whole point. A 1/2-cup side of cooked beans (86 g) carries about 20 g of total carbohydrate, which sounds like a lot. But almost 7.5 g of that is fiber, and fiber doesn’t behave like a carb in your body. Subtract it and you land at roughly 13 g of net carbs — the number that actually matters if you’re counting. Per 100 g the totals are 23.7 g carbs, 8.7 g fiber, leaving 15 g net.
Why net carbs are so much lower than total
Net carbs are simply total carbs minus fiber, and black beans have one of the largest total-to-net gaps of any everyday food. More than a third of their carbohydrate is fiber — the indigestible part that passes through without being broken down into blood sugar. So while the label-style total reads ~20 g per 1/2 cup, the digestible, blood-sugar-relevant load is closer to 13 g. This is the heart of the “beans aren’t as carby as they look” story: a heaping scoop of black beans and a half-cup of white rice can show similar total carbs, but the beans deliver a fraction of the usable starch and a wall of fiber the rice doesn’t have. There’s almost no sugar in the mix either — about 0.3 g per 1/2 cup — so what you’re counting is starch, heavily offset by fiber.
What this means for keto, low-carb, and blood sugar
For keto, black beans are borderline — net carbs are the deciding factor. At ~13 g net per 1/2 cup, they’d eat most of a strict 20 g keto budget, so they’re a “small portion, occasionally” food at that level. On a moderate low-carb plan, they fit comfortably: 13 g of net carbs buys you a serving loaded with fiber and around 7–8 g of protein, which is a good trade. For anyone watching blood sugar, the same fiber that lowers net carbs also slows digestion — black beans have a relatively low glycemic index and produce a slower, flatter blood-sugar rise than starchy staples. That makes them one of the more diabetic-friendly carbohydrates, as long as the portion stays honest.
Black beans aren’t just a carb to manage, though — they’re a genuine protein-and-fiber food. If you want that side of the picture, see protein in black beans. And for any packaged or canned version, read the label’s own carb and fiber lines, since net carbs depend on both.
Frequently Asked Questions
How many carbs are in 1/2 cup of black beans?
About 20 g of total carbohydrate in a 1/2-cup serving of cooked black beans (86 g), which is 23.7 g per 100 g (USDA FDC 173735). But that total is misleading on its own — almost 8 g of it is fiber, so the number that counts for low-carb eating is much lower.
What are the net carbs in black beans?
Roughly 13 g net carbs per 1/2 cup — total carbs (~20 g) minus the ~7.5 g of fiber. Fiber isn't digested into blood sugar, so net carbs subtract it out. Black beans have one of the biggest total-to-net gaps of any legume: more than a third of the carbohydrate is fiber, which is exactly why they 'aren't as carby as they look.'
Are black beans keto or low-carb?
They're borderline, and net carbs are the deciding factor. At ~13 g net per 1/2 cup, black beans are too high for a strict 20 g keto day in any real quantity, but they fit a moderate low-carb plan well — a 1/2-cup side leaves room, and you get a lot of fiber and protein for those carbs. Count the net number, not the total.
Do black beans spike blood sugar?
Less than their carb count suggests. The high fiber content slows digestion, so black beans have a relatively low glycemic index and produce a gentler, slower blood-sugar rise than a starchy food like white rice or potato. The fiber, plus their protein, is why they're considered a diabetic-friendly carbohydrate when portioned sensibly.
How much fiber is in black beans?
About 7.5 g per 1/2 cup (8.7 g per 100 g) — a quarter or more of a day's worth from one side dish. That fiber is the whole story here: it's what makes net carbs (~13 g) so much lower than total carbs (~20 g), and what slows the food down in your gut.
When was this data last verified?
2026-06-04, against USDA FoodData Central FDC 173735 (Beans, black, mature seeds, cooked, boiled, without salt; SR Legacy). We re-verify reference pages periodically and update when USDA revises the entry.
Whole-food values are USDA reference data, not a Labelgrade (that score is for branded packaged products). See our methodology and the macro calculator to turn this into a daily target.