A medium ear of sweet corn — about 6¾ to 7½ inches long — contains roughly 27 grams of carbohydrates. That figure comes from USDA food composition data for one ear of raw sweet corn with the kernels cut off the cob, and it covers all three carb types: starch, natural sugars, and fiber.
If you are tracking carbs, the number you actually log depends on one thing: whether you count fiber. Of those 27 grams, about 2 to 3 grams are fiber. Most people tracking total carbs count all 27. People tracking net carbs subtract the fiber and land closer to 24 or 25 grams per ear.
Corn is not a vegetable in the nutrition sense. It is a grain, and its carb load reflects that.
What Exactly Counts As One Ear Of Corn?
Portion size is where most carb counts go wrong. The 27-gram figure applies to a medium ear. Corn comes in a wide range of sizes, and the difference between a small and a large ear is substantial.
A small ear, roughly 5½ to 6½ inches, contains around 19 grams of carbs. A large ear, about 7½ to 9 inches, contains closer to 33 grams. An extra-large ear can exceed 40 grams. That is a swing of more than 20 grams of carbohydrate depending on which ear you pick up.
Frozen and canned corn change the math too. A half-cup of canned whole kernel corn contains about 15 to 17 grams of carbs, depending on whether it is drained and whether sugar was added during processing. A half-cup of frozen corn kernels runs about 16 to 18 grams. Both are easier to measure precisely than a cob.
One more variable: how you cook it. Boiling does not meaningfully change the carbohydrate content, though it can leach small amounts of water-soluble nutrients into the cooking water. Grilling or roasting concentrates the natural sugars slightly through moisture loss, so the carbs per gram of edible corn go up a little — but the difference per ear is small.
How Many Carbs On Corn On The Cob Compared To Other Starchy Sides
Corn sits in the middle of the starchy side dish range. It is higher in carbs than most green vegetables and lower than a comparable serving of potato or rice.
| Food | Serving | Total Carbs | Fiber |
|---|---|---|---|
| Sweet corn on the cob | 1 medium ear | ~27 g | ~2–3 g |
| Baked potato | 1 medium | ~37 g | ~4 g |
| White rice, cooked | 1 cup | ~45 g | ~1 g |
| Green peas, cooked | 1 cup | ~25 g | ~9 g |
| Broccoli, cooked | 1 cup | ~11 g | ~5 g |
The comparison that matters most for blood sugar is not total carbs but how fast those carbs hit the bloodstream. Corn has a moderate glycemic index. It raises blood glucose faster than peas or broccoli but slower than white rice or a baked potato. The fiber content helps, though corn’s fiber is modest compared to legumes.
One nuance people miss: corn’s carbohydrate profile shifts as it sits after harvest. Sweet corn converts its sugars to starch over time. An ear eaten the day it is picked tastes sweeter and has a slightly different sugar-to-starch ratio than one that has been in a refrigerator for a week. The total carb count stays roughly the same, but the type of carb changes.
Does Corn Fit Into A Low-Carb Or Keto Diet?
Corn does not fit comfortably into a ketogenic diet. At roughly 24 to 25 grams of net carbs per ear, a single ear can consume most or all of a daily net carb allowance on a strict keto plan, which typically caps net carbs at 20 to 50 grams per day.
On a moderately low-carb diet — say 50 to 100 grams of net carbs daily — a half ear or a half-cup of kernels can fit, but it takes planning. The carb density is simply higher than most people expect from something they think of as a vegetable.
For people with type 2 diabetes managing blood glucose through diet, corn is not off-limits, but portion size matters. A half ear paired with protein and fat digests more slowly than a full ear eaten alone. That is standard guidance for any moderate-glycemic food, not something specific to corn.
For most healthy adults eating a balanced diet, 27 grams of carbs from an ear of corn is not a problem. It is a normal part of a meal that also contains protein and vegetables.
Why Corn’s Carbs Behave Differently Than You Might Expect
Corn contains a mix of starch and sugar, and the ratio depends on the variety and its freshness. Modern sweet corn varieties have been bred for higher sugar content — sometimes two to three times the sugar of older varieties. That is why supermarket corn tastes so sweet.
That sweetness affects flavor more than total carbohydrate. Whether the carbs come from sugar or starch, the total grams are similar. What changes is how quickly your body breaks them down. Sugars absorb faster. Starches take longer because digestive enzymes have to break them apart first.
The fiber in corn is mostly insoluble, which means it passes through largely undigested. It adds bulk and supports gut health, but it does not significantly slow glucose absorption the way soluble fiber from oats or beans does. This is a meaningful distinction. Corn’s fiber content is often cited as a reason it is “healthy,” but its fiber type does not provide the same blood sugar benefits as soluble fiber.
This is not a reason to avoid corn. It is a reason to be accurate about what corn does and does not offer nutritionally.
How To Measure Carbs On Corn On The Cob Accurately
If you need a precise count — for diabetes management, medication dosing, or a strict carb target — weighing is more reliable than eyeballing.
- One medium ear yields roughly 90 grams of edible kernels.
- That works out to about 0.3 grams of carbohydrate per gram of kernels.
- A half-cup of kernels weighs about 75 to 80 grams and contains about 15 to 17 grams of carbs.
- A full cup of kernels contains roughly 30 to 34 grams of carbs.
If you are eating corn off the cob, use a measuring cup. If you are eating it on the cob, use the ear size as a guide. Small, medium, and large ears differ enough that the distinction matters for anyone counting carefully.
Packaged frozen or canned corn lists carbs per serving on the nutrition label. That is the most accurate source for those products, because added sugars and brine vary by brand.
Is Corn High In Carbs Compared To Other Vegetables?
Yes, compared to most vegetables. Corn has roughly two to three times the carbs of green beans, zucchini, or peppers per equal serving. It belongs in the starch category alongside potatoes, peas, and winter squash.
That classification matters for meal planning. If you are building a plate with a starch, a protein, and a non-starchy vegetable, corn is the starch — not the vegetable. Treating it as a free vegetable is one of the most common carb-counting mistakes.
Peas are a useful comparison. A cup of cooked green peas has about 25 grams of carbs, similar to a medium ear of corn, but nearly 9 grams of fiber. That fiber difference changes the net carb picture considerably: peas land around 16 net carbs per cup, while corn lands around 24 per ear.
Neither food is better or worse in absolute terms. They just behave differently in the body, and knowing which category a food falls into helps you plan a meal that matches your goals.
Frequently Asked Questions
How many carbs are in one ear of corn on the cob?
A medium ear of sweet corn contains about 27 grams of total carbohydrates, including 2 to 3 grams of fiber. A large ear can contain 33 grams or more.
How many net carbs are in corn on the cob?
A medium ear has roughly 24 to 25 grams of net carbs after subtracting fiber. Net carbs are calculated by subtracting total fiber from total carbohydrates.
Is corn on the cob a carb or a vegetable?
Corn is botanically a grain and nutritionally classified as a starchy food, not a non-starchy vegetable. It has a carb content similar to peas or potatoes.
Can diabetics eat corn on the cob?
Corn can fit into a diabetes meal plan, but portion size matters because it has a moderate glycemic index. A half ear paired with protein and fat is a common approach, though individual carb targets vary and should be discussed with a healthcare provider.
