Raw and cooked Onion both contains about 9-10% carbohydrate content. Carbohydrates in Onion mainly consist of simple sugars, such as glucose, fructose and sucrose, as well as fibers. About 100 grams of Onion has 9.3 grams of carbohydrates and 1.7 grams of fiber, so the total digestible carbohydrate content is 7.6 grams.