The USDA Nutrition Database indicates that a medium carrot contains 25 calories. A large carrot that is between 7 1/4 to 8 1/2 inches long contains 30 calories. A small carrot that is 5 1/2 inches long has 20 calories.
In addition to 25 calories, a medium carrot provides approximately 6 grams of carbohydrates and 2 grams of fiber. Carrots contain several vitamins and minerals but are well known for their large quantities of Vitamin A, which is required for good vision. They also contain large quantities of beta carotene, which is converted to Vitamin A. According to WebMD, eating a carrot provides 200 percent of the daily Vitamin A requirement.
Other important nutrients found in carrots are fiber, vitamin K, potassium, molybdenum, vitamin C and the B complex vitamins.