Most non-starchy vegetables contain between 3 and 8 grams of carbohydrates per serving, while starchy vegetables like potatoes and corn pack around 15 grams or more. The range is wide enough that your choice of vegetable can meaningfully affect your daily carb intake, especially if you’re watching your blood sugar or following a low-carb diet.
Low-Carb Vegetables (Under 6 Grams per Serving)
Leafy greens and watery vegetables sit at the bottom of the carb spectrum. A cup and a half of shredded leaf lettuce has roughly 2 grams of carbs. Celery, cucumbers, and radishes are similarly low, all coming in under 4 grams per serving. These vegetables are so low in carbohydrates that organizations like Diabetes Canada don’t even assign them a glycemic index value.
Other vegetables that fall into this low range include asparagus (about 4 grams for 5 spears), mushrooms (around 3 grams for 5 medium caps), and green cabbage (about 4 grams for a wedge of a medium head). Broccoli and cauliflower hover around 5 to 6 grams per serving. If you’re counting carbs strictly, these are essentially “free” vegetables that you can eat in generous portions without much impact on your totals.
Moderate-Carb Vegetables (6 to 12 Grams)
The middle range includes many everyday vegetables. A medium tomato contains about 7 grams of carbs. A medium bell pepper has roughly 7 to 8 grams. Green snap beans come in around 7 grams for three-quarters of a cup. These are still relatively low numbers, but they add up if you’re eating multiple servings in a meal.
Carrots and onions also land in this range, though their sugar profile is worth noting. Raw carrots contain relatively little sugar per 100 grams (less than 1 gram each of fructose and glucose), with the rest of their carbs coming from fiber and starch. Raw onions, by contrast, carry nearly 4 grams of simple sugars per 100 grams, which is why they caramelize so easily when cooked. A whole medium onion (148 grams) has about 10 grams of total carbs. In practice, most people use a fraction of an onion at a time, so the actual carb contribution per dish is small.
Starchy Vegetables (15 Grams and Up)
Starchy vegetables are in a different league. According to standardized nutrition lists used in diabetes meal planning, a single serving of any starchy vegetable delivers about 15 grams of carbohydrate, which is equivalent to one slice of bread. But the serving sizes are smaller than most people realize:
- Potato (baked with skin): 15 grams of carbs in just one-quarter of a large potato (about 3 ounces)
- Potato (boiled or mashed): 15 grams per half cup
- Sweet potato or yam: 15 grams per half cup
- Corn: 15 grams per half cup of kernels, or half a large cob
- Green peas: 15 grams per half cup
A whole medium potato (148 grams) contains closer to 35 grams of total carbohydrates. A whole medium sweet potato (130 grams) has around 26 grams. A full ear of corn comes in near 17 to 19 grams. If you’re eating a baked potato as a side dish, you’re likely consuming two to three “servings” of starchy carbs in one sitting.
Net Carbs vs. Total Carbs
Many people subtract fiber from total carbohydrates to calculate “net carbs,” since fiber passes through the digestive system largely undigested and has minimal effect on blood sugar. The formula is simple: total carbs minus fiber equals net carbs.
This distinction matters most for vegetables that are high in fiber relative to their total carbs. Broccoli, for example, has about 5 to 6 grams of total carbs per serving but roughly 2 to 3 grams of fiber, cutting its net carbs nearly in half. Raw carrots contain about 2.4 grams of insoluble fiber per 100 grams plus another 0.5 grams of soluble fiber, which brings their net carb count down noticeably. Starchy vegetables have fiber too, but their total carb count is high enough that the reduction is proportionally smaller.
Cooking also changes the picture slightly. Cooked carrots have more soluble fiber (1.6 grams per 100 grams) compared to raw (0.5 grams), while their insoluble fiber stays about the same. The total carb count shifts a bit with cooking as well, since heat breaks down cell walls and concentrates nutrients as water evaporates.
How Vegetables Affect Blood Sugar
Total carb count isn’t the only factor that determines how a vegetable affects your blood sugar. The glycemic index measures how quickly a food raises blood glucose on a scale from 0 to 100, and vegetables span the full range.
Cooked carrots, green peas, sweet potato (boiled or steamed), and winter squash all have a low glycemic index (55 or under), meaning they raise blood sugar gradually. Corn, beets, parsnips, pumpkin, and cooled cooked potatoes fall in the medium range (56 to 69). Hot freshly cooked potatoes, instant mashed potatoes, and baked sweet potatoes rank high (70 or above), causing a faster spike.
That last detail catches people off guard: the same vegetable can shift categories depending on how you prepare it. A boiled sweet potato has a low glycemic index, but baking or frying it pushes it into the high range. A potato that’s been cooked and then cooled (as in potato salad) has a lower glycemic index than one eaten hot, because cooling converts some of the starch into a form that resists digestion. Yams follow the same pattern: steamed or boiled, they’re medium; roasted or mashed, they jump to high.
Practical Portion Guide
For everyday planning, it helps to group vegetables into rough tiers. Non-starchy vegetables like leafy greens, peppers, broccoli, cauliflower, cucumbers, and celery are low enough in carbs that most people don’t need to measure them carefully. A large mixed salad with several cups of these vegetables might total 8 to 12 grams of carbs.
Root vegetables and tomatoes occupy a middle tier where portions start to matter. A couple of carrots, half a medium onion, and a tomato in a stir-fry could add 12 to 15 grams of carbs to the dish. That’s not a problem for most people, but it’s useful to know if you’re aiming for a specific daily target.
Starchy vegetables need the most attention. Half a cup is the standard portion that delivers 15 grams of carbs, and most restaurant or home-cooked portions are two to three times that size. If you’re building a plate and want to keep carbs moderate, treat starchy vegetables the way you’d treat rice or bread: as a measured portion rather than an unlimited side.