A handy resource: King Arthur Baking
Try to use a refrigerated starter at least once a week. Replace the used amount of starter (by weight) with 1/2 whole wheat pastry or unbleached flour and 1/2 water (by weight). For example, 60 grams water, 60 grams flour.
Use or feed a non-refrigerated starter every two days or so.
To replace flour and liquid in any recipe with sourdough starter:
Adding sourdough to a recipe
Notes: 1 cup flour = 120-130 grams = 4.25 – 4.5 ounces
1 cup whole wheat flour = 130-156 grams = 4.5-5.5 ounces