Weigh food before or after cooking?

If you weigh something raw, use an entry for raw meat (i.e., chicken, breast, meat only, raw). If you weigh something cooked, use an entry for cooked meat and the manner of cooking (i.e., chicken, breast, meat and skin, cooked, roasted).

Both are perfectly fine if you choose the right entry. Depending on how you are cooking them, it might require one or the other. For example, if making a stew involving boneless chicken thighs, you will want to make a recipe for the stew (unless you are the only one eating it) and weigh the components, including the chicken, before cooking. But if you are cooking bone-in meat (say, a chicken breast with bones in, skin on, or, perhaps, a whole turkey), you will likely find it easier to weigh the meat you eat cooked and that's fine if you use a cooked entry.