We don't actually need any carbs, just protein for our body maintenance and repair and fat for energy. However we do need a small amount (approx 130g) of glucose for some parts of our brain to function, and our livers are designed to generate this for us if required.
Experience and my meter have taught me that my body is comfortable with a range of around 20-50g carbs a day, so this is what I've chosen long term to enable me to both eat a variety of suitable food and to keep my glucose at high end of normal/low pre-diabetic levels. But this is entirely personal, and we all need to use our meters to find how many carbs we can tolerate or how many we can choose to eat and keep our glucose within an appropriate range.