When it comes to determining how much a fluid ounce of water will weigh, keep the following in mind. A fluid ounce of water weighs about 1.043 dry ounces. This is the same as 0.0652 pounds or 29.574 grams. The weight may differ if the liquid has any type of saturation to it. The density of water is 1 av oz per fluid ounce. If the substance is not water, the weight will vary significantly based on the density of the fluid itself.