What is how much does 16oz water weigh?

The weight of 16 fluid ounces of water is approximately 1 pound. This is because the density of water is roughly 1 ounce per fluid ounce, meaning that each fluid ounce of water corresponds to about 1 ounce (avoirdupois) of weight. Keep in mind that this measurement is based on water at its maximum density, which occurs at around 39.2°F (4°C), and that the weight can vary slightly with temperature due to changes in water density.