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.