adding new food

c1aireee

i am rubbish at maths & I am trying to add a dessert which is not recognised by MFP ( cos when I scanned the barcode it came up a Pizza Hut Banoffee cake??? ) , so if the dessert information is values are per 100g what is the maths to get 120g values like calories fat etc... which is how big the dessert is? thanks in advance