One medium ear of corn on the cob (about 6 3/4" to 7 1/2" long, weighing approximately 103 grams) contains roughly 22 grams of total carbohydrates, including about 2.6 grams of fiber, resulting in about 19.3 grams of net carbs

. Another source states one ear has about 19 grams of carbohydrates with 2 grams of fiber

. For a larger serving size, such as 1 cup of corn cob (about 145 grams), the total carbs increase to about 27 grams with around 2.9 grams of fiber

. In summary:

• Medium ear (103g): ~22g total carbs, ~19g net carbs
• 1 cup (145g): ~27g total carbs, ~24g net carbs

The carbs in corn mostly come from starch and sugars, with fiber helping to moderate blood sugar impact