Question: how many grams is 1/2 cup of sourdough starter?
Answer: Either way, discard half the starter (113 grams, about 1/2 cup), and add to the remainder a scant 1 cup (113 grams) King Arthur Unbleached All-Purpose Flour, and 1/2 cup (113 grams) cool water (if your house is warm); or lukewarm water (if it's cold).