I agree it is difficult for us Brits to comprehend measuring things like lettuce by volume. How much you squish it down could double the amount ............

There is a good way to find out how much a US cup is reckoned to hold of any particular food item. Go to http://www.nal.usda.gov/fnic/foodcomp/search/
and type in the food you want. Say cauliflower. The page it returns will give you options such as raw or cooked etc. Select one and the next page will tell you how much 1 cup of this items weighs in grams. Raw cauliflower happens to be 100g per cup

Happy converting!

neo_crone