One cup of raw blackberries (about 144 grams) contains roughly 13.8 grams of total carbohydrates, 7.6 grams of fiber, and only 6.2 grams of net carbs. That makes blackberries one of the lowest-carb fruits available, on par with raspberries and noticeably lower than blueberries or strawberries.
Full Carb Breakdown Per Serving
Here’s what a standard 1-cup serving of raw blackberries looks like nutritionally:
- Total carbohydrates: 13.8 g
- Dietary fiber: 7.6 g
- Net carbs (total carbs minus fiber): 6.2 g
- Sugars: about 7 g
- Calories: 62
If you’re measuring a smaller portion, 100 grams of raw blackberries (roughly two-thirds of a cup) has about 9.6 grams of total carbs, 5.3 grams of fiber, and 4.3 grams of net carbs.
Why the Fiber Content Matters
Blackberries pack more fiber per calorie than almost any other common fruit. That 7.6 grams of fiber per cup is about 27% of the daily recommended intake. Most of it is insoluble fiber, the kind that supports digestion and keeps things moving. A smaller portion is soluble fiber, which slows sugar absorption and helps moderate your blood sugar response after eating.
Because fiber isn’t digested and doesn’t raise blood sugar, net carbs give you a more accurate picture of how blackberries actually affect your body. At just over 6 grams of net carbs per cup, blackberries fit comfortably into low-carb and keto diets, where most people aim for 20 to 50 grams of net carbs daily.
What Types of Sugar Are in Blackberries
The sugars in blackberries are split almost evenly between glucose and fructose, with a trace of sucrose. Per 100 grams of fresh fruit, blackberries contain about 2.3 grams of glucose, 2.4 grams of fructose, and less than 0.1 grams of sucrose. This near-absence of sucrose (table sugar) is unusual among fruits and contributes to that characteristic tart flavor.
The roughly even glucose-to-fructose ratio means your body processes the sugars through two different pathways, which tends to produce a more gradual blood sugar rise compared to fruits that are fructose-dominant.
Glycemic Index and Blood Sugar Impact
Blackberries have a glycemic index of 25, which is considered low. For context, anything under 55 is classified as low-GI, and most tropical fruits land in the 50 to 70 range. The glycemic load, which accounts for actual portion size, is only 4. A GL under 10 is considered low, so blackberries barely register in terms of blood sugar impact.
The pigments that give blackberries their deep purple-black color also play a role here. These compounds have been shown to improve how the body handles insulin and blood sugar. In animal studies, blackberry pigment extracts significantly improved insulin sensitivity and restored normal glucose tolerance, even in subjects on high-fat diets. The effect appears to work partly through changes in gut bacteria that influence metabolism.
Fresh vs. Frozen Blackberries
Unsweetened frozen blackberries are slightly higher in carbs than fresh. Per 100 grams, frozen blackberries contain about 15.7 grams of total carbohydrates and 5 grams of fiber, giving you roughly 10.7 grams of net carbs. That’s more than double the net carbs of the same weight in fresh berries.
The difference comes down to water loss. When blackberries are frozen and thawed, they lose some moisture, concentrating the sugars and carbs by weight. You’re essentially getting more fruit per gram. This doesn’t mean frozen blackberries are unhealthy, but if you’re counting carbs closely, weigh your portions rather than relying on cup measurements, since frozen berries pack more densely into a cup than fresh ones do.
How Blackberries Compare to Other Berries
Among common berries, blackberries and raspberries consistently rank lowest in net carbs. Here’s how one cup of each compares:
- Blackberries: 6.2 g net carbs
- Raspberries: 6.7 g net carbs
- Strawberries: 8.7 g net carbs
- Blueberries: 17.4 g net carbs
Blueberries contain nearly three times the net carbs of blackberries per cup, which surprises many people who consider all berries roughly equivalent. If you’re choosing a fruit for a low-carb diet, blackberries give you the most volume for the fewest carbs.