Have you ever looked at a soft drink can and wondered how much 12 oz weighs? Here is the answer in ounces, pounds, and grams and a look at how you do the calculation.
- 12 ounces of water is really 12 fluid ounces.
- Ounces (oz) and fluid ounces (fl oz) don’t have the same weight.
- 12 fluid ounces of water is about 12.5 ounces.
- It is about 0.78 pounds (lb).
- 12 fluid ounces is around 354 grams (g).
The Difference Between Ounces and Fluid Ounces (Oz and Fl Oz)
You measure water and other liquids in fluid ounces (fl oz) and not ounces (oz). A fluid ounce is a measure of volume, while an ounce is a unit of mass or weight. An ounce of water weighs slightly more than a fluid ounce:
1 fl oz = 1.043 oz
or
1 oz = 0.96 fl oz
For small volumes of water, like you use in cooking recipes, the two values are close enough that they are interchangeable. However, the conversion between a density and a mass (or weight) depends on density. Density varies, depending on the liquid. For example, 12 fl oz of vegetable oil weighs less than 12 fl oz of water.
Dry ingredients often are measured in ounces or grams because their volume depends on how compacted they are.
Finding How Much 12 oz of Water Weighs
The math for finding how much 12 oz of water weighs is straightforward using unit conversions.
weight of 12 fl oz water = 12 fl oz x 1.043 oz/fl oz = 12.516 oz
Once you have the weight of water in ounces, converting to pounds and grams is simple:
1 lb = 16 oz
weight of 12 fl of of water = 12.516 oz / 16 oz/lb = 0.782 lb
1 lb = 453.592 g
weight of 12 fl oz of water = 0.782 lb x 453.592 g/lb = 354.709 g or about 355 g
Of course, if you’re really wondering how much a can of soda or soup weighs, you need to factor in the weight of the can. This brings the number up a bit, but it’s still somewhat less than a pound or half of a kilogram.
If you search online for the answer to the question, you’ll see slight variations in the values. The last digit depends on how many significant figures you carry in the calculation. Really, all of these numbers are estimates because they are based on a single value for the density of water. Density varies according to temperature. The density of pure water is about about 1 gram per milliliter (g/ml), 1 gram per cubic centimeter (g/cm3), 1000 kg/m3, or 62 pounds per cubic foot (lb/ft3). At normal temperatures, it’s slightly less.
How to Convert Fluid Ounces to Grams
If you are serious about getting an exact value, include density in the calculation.
grams = fluid ounces x 29.57353 g/fl oz x ingredient density
For example, at 80 °F, the density of pure water is 0.99669 g/ml.
For 12 fluid ounces of water at 80 °F:
grams = 12 x 29.57353 x 0.99669 = 353.708
Cooking oil has a density around 0.88 g/ml. The weight of 12 fluid ounces of cooking oil is:
grams = 12 x 29.57353 x 0.88 = 312.2965