An ounce of water weighs approximately 28.35 grams. This is based on the fact that one fluid ounce of water is defined as 29.5735 milliliters and the density of water is about 1 gram per milliliter at room temperature. Therefore, when you convert fluid ounces to grams, you use the same numerically equivalent figure, with a slight adjustment for the liquid volume measurement.
To clarify, if you take one ounce of liquid water, you can expect it to weigh nearly 28.35 grams. This weight is slightly less than an ounce due to the differences in measuring fluid volume and weight, but for practical purposes, it’s often rounded to 28 grams.