Carbohydrates should comprise 45-65% of total calories, added sugar should
not exceed 10%, and women need 25 grams of fiber a day. For instance, if you required 1500 calories and chose to have 55% of your calories from carbohydrates, you would need
206 grams of total carbohydrate, no more an 37 grams of carbohydrate from added
sugar, and 25 grams of fiber.
To find "net carbs", subtract the grams of fiber from the grams of total carbohydrate, and so, in the example, the net carb goal would be 181 grams/day "Net carbs" is a term invented by the food and diet industry. It has no scientific or legal meaning.