Yes, weighing your food is perfectly fine and will give you an accurate measurement compared to filling a measuring cup with awkward shaped vegetables. A ½ cup of vegetables is about 85 grams. If you are away from home, you can always look up how many carrot slices for instance would count as a serving at: ChooseMyPlate.gov. However, the easiest method for determining how many fruits and vegetables to eat, is to use the half your plate method. By making half your plate fruits and vegetables you remove any guess work in figuring out serving sizes, especially since active men need a few more and inactive women need less.