By Staff Writer | Last Updated August 4, 2015
An ounce is a standard unit of measurement commonly used in the US Customary and British Imperial systems to measure mass, weight and volume. There are different methods for measuring an ounce depending on the item being measured. For example, an ounce of water is measured in fluid ounces while an ounce of flour is measured in ounce-force. A troy ounce is used for measuring precious metals or monetary coins. Let’s take a closer look at the three main types of ounce measurements in use around the world.
History of the Weights and Measures System
The Weights and Measures System is a system that was first implemented to ensure accuracy for monetary purposes. Ancient Romans used grains of wheat to measure coins during their time. This was used until the 1400s when King Henry II adopted the Troy weight system. Britain acknowledge and implemented the troy weight system in the early 1500s.
The English that traveled to the new world understood and followed the troy weights and measurements system. In 1828, this method of weighing and measuring money and weight was adopted in the United States. This is where the idea of 437.5 grains are equivalent to one standard ounce-force.
While the troy ounce is recognized as being one-twelfth of a pound, the ounce force equates to one-sixteenth of a pound. This does create a discrepancy for a standardized weights and measurements system. That is why the ounce is labeled as either being an ounce-force, fluid ounce or troy ounce.
An ounce-force is equivalent to one-sixteenth of a pound. This is used to measure the weight of an object. It is also equal to 437.5 grains and 28.35 grams. Some examples of items that weigh an ounce under these standards include:
- AA battery
- CD case
- CD without the case
- Five quarters
- Regular-size letter
- Slice of bread
- Standard ink pen
A fluid ounce is a unit of measurement that measures the volume of an object. In the US, a fluid ounce is equivalent to one-sixteenth of a pint or 29.6 milliliters. In Britain, a fluid ounce equates to one-twentieth of an imperial pint, or 28.4 milliliters. The abbreviation of the fluid ounce is fl.oz. Some examples of a fluid ounce include:
- One-eighth cup of water
- Six teaspoons of honey
- Two tablespoons cough syrup
Other common items that are often measured in ounces include milk, coffee, soft drinks, juice and canned food. Liquid household cleaners such as bleach and laundry detergent are also measured in fluid ounces.
A troy ounce was originally called an apothecary’s ounce. This was due to it being the standard unit of measurement for medicine many centuries ago. While the apothecary ounce follows the grain measurement, the troy ounce is truer to the pound. For example, 20 grains is equivalent to 1 scruple; 3 scruples are equal to 1 dram; 8 drams equal 1 ounce. Medicine is dispensed along these measurements. A troy ounce is more commonly used for measuring metals and currency in countries such as Great Britain. Such as an ounce of gold or silver. A true troy ounce is equivalent to 31.12 grams while an ounce-force is equivalent to 28.35 grams.
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