How this calculator works
A fluid ounce is a volume and a pound is a mass, so there is no single factor between them. A US fluid ounce is 29.5735295625 mL and a pound is 0.45359237 kg, so the liquid density decides how many fluid ounces make one pound. The page multiplies the volume by the density to get mass, or divides the mass by the density to get volume. The preset densities are typical room temperature values: water is 1,000 kg/m3, milk 1,030, honey 1,420 and cooking oil 920, while diesel and gasoline vary with grade and temperature. Use the custom density for any other liquid.
Formula
mass = volume x density. pounds = fluid ounces x 29.5735295625 mL x density / 453.59237 g per pound. US fluid ounces = pounds x 453.59237 / (29.5735295625 x density).
Worked example
16 US fl oz of water is 473.176 mL, or 0.473176 kg, which is 1.04318 lb. The same 16 US fl oz of honey at 1,420 kg/m3 is 0.671910 kg, or 1.48131 lb. One pound of water is 15.3378 US fl oz. Imperial fluid ounces are smaller, so one pound of water is 15.9593 imperial fl oz.
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Frequently asked questions
Why is a fluid ounce not equal to an ounce?
A fluid ounce measures volume and an ounce measures mass. For water at room temperature one US fluid ounce weighs about 1.043 oz, so the two happen to be close, but for honey a fluid ounce weighs about 1.48 oz.
Is this a US or an imperial fluid ounce?
Both are offered. A US fluid ounce is 29.5735295625 mL and an imperial fluid ounce is 28.4130625 mL, about 4 per cent smaller, so the mass of a given number of imperial fluid ounces is lower.
How accurate are the preset densities?
They are typical values for a moderate room temperature. Real liquids vary with temperature and grade: diesel alone ranges from about 820 to 845 kg/m3. Enter the density from your supplier or a hydrometer reading for a precise answer.
Does the answer change with temperature?
Yes. Most liquids expand when warmed, which lowers the density, so the same volume weighs a little less when hot. Water is most dense at about 4 degrees Celsius, near 1,000 kg/m3.