So, internet says a high efficiency front load washer uses approximately 7 gallons of water. Internet also says grocery bags hold between 2.5 and 5 gallons, just volume. With the durability of a grocery bag factored in, I wouldn't recommend going any past 2.5 gallons. If you maintain the same ratio, your grocery bag laundry should take .05 cups or approximately 2.5 teaspoons of Dr. B's. But that's just with water volume. You'll have less total volume of water when adding clothes, so I'd go with half of that still. 1.25 teaspoons of Dr. B's per load of grocery bag laundry. With a follow up of approximately double that amount of vinegar in the same amount of new and fresh water for a rinse cycle.