A thumb (or knuckle) length piece (about 3 inches) weighs about 1 ounce; this means one thumb contains about 2 teaspoons (about 6 grams). One tablespoon equals 4 teaspoons but since one teaspoon weighs 5 grams there are actually 3 tablespoons per thumb! So 1/2 cup chopped ginger = 15 thumbs = 75 tablespoons!