at first calculating carbs can look quite hard but really it is very simple.
what i do is look at the back of food packs,for the nutiritional bit.
here u will find all the info.
there is 4 calories per gram of carbs,so to get a extra 500 calories a day.
u would need to eat 125 grams of carbs.
in a 100 grams of brown rice there is about 70 grams of carbs(depending on the make u buy)
just basically calculate it to the desired amount u need,
a good set of scales is a must.
rice and pasta are quite similar in content i think(i only eat rice)
im unsure about potatoes,
it might say on the pack u buy.
i hope this helps draps
probably sound like a load of mumbo jumbo
steve