It isn't just how many carbohydrates you eat that counts in a healthy diet, it's what kind you choose. Nutritionally, carbs range from super-healthy to almost useless.
This number assumes that you're consuming an adequate number of calories per day, that you're within a normal weight range for your height, and that you are moderately active and in good health.
Caution: These estimates may not be appropriate for pregnant and nursing women.