How do you calculate how many cups are in 4 oz of water?

Generally, we all know that 1 cup is equal to 8 fluid ounces; if we calculate the number of cups in 4 fluid ounces of water, divide 4 by 8:

4 fluid ounces / 8 fluid ounces per cup = 0.5 cups

Hence, 4 fluid ounces of water is equivalent to roughly 0.5 cups.