In order to fulfill the mitzvah of consuming a festive meal on Shabbos or yom tov, a healthy person must eat at least a kebaitza-sized portion of bread at any point during his or her meal. A kebaitza is measured by visual size, not weight, so the amount of bread that you need to eat will depend on how fluffy your bread comes out. Your portion of bread should be at least the visual size of two eggs to qualify as a kebaitza. You’ll need to eyeball it! For multipurpose dough, I usually find that 70 grams of dough is sufficient for at least a kebaitza’s worth of baked bread. Artisan dough is trickier to predict, but a typical baked loaf normally yields about 10-12 portions that are each at least a kebaitza.