The fluid ounce is a measure of volume rather than weight. There are 16 fluid oz. to a pint in the U.S. customary system, and 20 fluid oz. to a pint in the Imperial system used elsewhere in the world. An Imperial fluid ounce weighs exactly 1 oz., so conversion between volume and weight is not necessary. A customary fluid ounce of water weighs slightly more than 1 oz., but converting from volume to weight is a simple process.
Enter the value in fluid ounces into the calculator. Check the calculator display to make sure you entered it correctly.
Multiply by 1.043, the weight of 1 fluid oz. of pure water. The result is the weight of the water.
Check for errors. Divide the result from Step 2 by 1.043. If the result does not equal the value obtained in Step 2, an error occurred. Repeat the calculations until the results match.
For most purposes, it is safe to assume that the weight of 1 fluid oz. of pure water equals an ounce.
The values are for pure water at standard temperature and pressure. Water such as seawater, containing dissolved solids, does not weigh the same as pure water.