A cup of fresh grapes contains about 16 grams of carbohydrates, with 15 of those grams coming from natural sugars and 1 gram from fiber. That’s based on a 92-gram serving, which is roughly a small handful. Larger cup measurements (around 150 grams) push closer to 27 grams of carbs, so the exact count depends on how generously you fill the cup and the size of the grapes.
Carbs by Serving Size
Because grapes are small and easy to snack on mindlessly, it helps to know the numbers at different portion sizes. A serving of about 10 grapes contains roughly 9 grams of carbohydrates. A loosely packed cup (92 grams) has 16 grams. A fully packed cup (151 grams) lands around 27 grams. Nearly all of those carbs are sugar, with only about 1 gram of fiber per cup, so the net carb count is almost identical to the total.
The sugars in grapes are primarily glucose and fructose, which are absorbed quickly. There’s very little starch or complex carbohydrate involved, which is why grapes taste noticeably sweet compared to many other fruits.
Red, Green, and Black Varieties
The carb differences between grape colors are minimal. Red, green (Thompson seedless), and black grapes all fall in the same range of 16 to 18 grams of carbs per 100 grams. Green grapes can taste slightly more tart, but their sugar content is comparable. Concord grapes, the deep purple variety used in grape juice and jelly, are similar as well. If you’re tracking carbs, the variety matters far less than the portion size.
Glycemic Index and Blood Sugar
Grapes have a glycemic index of around 46, which places them in the low GI category (under 55). That’s lower than watermelon, pineapple, and ripe bananas. The glycemic load, which accounts for how much you actually eat in a sitting, is about 4 for a 10-grape serving and around 12 to 13 for a full cup of 151 grams. A glycemic load under 10 is considered low, and over 20 is high, so a moderate portion of grapes produces a moderate blood sugar response.
For people managing blood sugar, the practical takeaway is that a small handful of grapes is unlikely to cause a significant spike, but eating a large bowl can add up quickly. Pairing grapes with a source of protein or fat, like cheese or nuts, slows digestion and flattens the blood sugar curve.
Grapes on a Low-Carb or Keto Diet
Grapes are one of the higher-carb fruits, which makes them tricky for strict low-carb eating. A single packed cup can deliver 26 to 27 grams of carbs, potentially using up an entire day’s carb allowance on a ketogenic diet (typically 20 to 50 grams per day). Most keto guides recommend avoiding grapes altogether or limiting them to a very small portion, around 10 to 15 grapes at most.
If you’re on a more moderate low-carb plan (under 100 grams per day), grapes fit comfortably in reasonable portions. A half-cup adds about 8 to 13 grams of carbs depending on how you measure, leaving plenty of room for other foods.
Fresh Grapes vs. Raisins
Drying grapes into raisins concentrates the sugar dramatically. Fresh grapes contain about 15% total sugars by weight. Raisins contain roughly 68 to 80% sugar by weight, a four- to five-fold increase in sugar density. The fructose content alone jumps from about 8% in fresh grapes to nearly 32% in raisins, and glucose follows the same pattern.
This means a small box of raisins (about 43 grams) packs around 29 grams of carbs, nearly double what you’d get from a loosely filled cup of fresh grapes that weighs twice as much. If you’re watching carb intake, fresh grapes are significantly easier to manage than raisins simply because the water content fills you up before the sugar adds up.
How Grapes Compare to Other Fruits
- Strawberries: About 8 grams of carbs per cup, roughly half the carbs of grapes
- Blueberries: About 21 grams per cup, slightly more than grapes
- Apple (medium): About 25 grams, comparable to a packed cup of grapes
- Banana (medium): About 27 grams, similar to grapes cup for cup
- Watermelon: About 11 grams per cup, lower than grapes despite tasting very sweet
Grapes sit in the middle of the fruit spectrum for carbs. They’re not as low-carb-friendly as berries, but they’re not as dense as bananas, mangoes, or dried fruits. For most people eating a balanced diet, a cup of grapes is a perfectly reasonable snack that contributes vitamins, antioxidants, and hydration alongside its sugar content.