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Difference Between Fluid Ounces and Ounces

Fluid Ounces vs Ounces

There’s a lot of ongoing confusion between the terms “fluid ounces” and “ounces.” This is because there is a variety of system measurements used across the world like the Metric System, English, U.S. Customary, Imperial, Natural Units, and Non-Standard Units. Moreover, one has to discern if the item being measured is in liquid form or in dry form because the measurement of weight and volume are two different things.

In this connection, two measurements are often misused by many – the fluid ounce and the ounce. In its simplest possible explanation, a fluid ounce (abbreviated as fl. oz.) is used to measure fluids while an ounce (abbreviated as oz.) is for dry measurements. This gives us the idea that a fluid ounce is a measurement of volume while the other is a measurement of weight.

In common applications, most are aware how big a common household pint is. One pint (an English unit of measurement) is actually equal to 16 fluid ounces (U.S. Customary). Another example is the pound (a common U.S. Customary or Imperial Unit). One pound (abbreviated as lb.) is equal to 16 ounces. It is hard to overlap or connect the measurements of a fluid ounce (volume) to an ounce (weight). This means that it is not possible to immediately determine the weight of a certain matter only from a given volume, per se. You first need to identify the density of the liquid to know its weight. So converting a fluid ounce to weight units should include density in the formula. If we’re talking about one fluid ounce of water, its corresponding ounce is approximately 1.043 – giving about a 1:1 ratio. But in other liquids, the difference may become very significant.

The term “ounce” is of Latin origin from the word “uncia” which means “a twelfth part.” It can also be used in several different systems of measurements, but the most widely used systems for “ounce” is the international troy ounce and the international avoirdupois ounce. This suggests that one avoirdupois ounce is approximately 28.3495231 grams. Similarly, we use two systems in measuring fluid ounces. For example, one unit of a fluid ounce is approximately 29.5735297 ml. using the U.S. Customary system while it is just approximately 28 ml. using the Imperial system. This makes one beg for the use of one unified, standard system of measurement which is not entirely applicable today.


1.“Ounce” has an “oz.” abbreviation while “fluid ounce” is abbreviated as “fl. oz.”
2.An ounce is measuring weight while a fluid ounce is measuring volume.
3.One pound is equal to 16 ounces while one pint is equal to 16 fluid ounces.
4.One fl. oz. is equal to 29.5735297 ml. using the U.S. Customary system.
5.One “oz.” is approximately 28.3495231 grams using the international avoirdupois system.

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  1. Very well, thoroughly done.

    Retired meteorologist.

  2. Well there is a “one unified, standard system of measurement”, simple and easily comprehensible, based on 10’s not 12’s or 16’s and it is “entirely applicable today” around the whole world, it is called the metric system.

  3. Sorry for making everyone wait so long to hear what I have to say… The metric system great an all, but a Base 12 number system would be more beneficial than a Base 10. Where’s your God now???

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