# What is a customary unit of weight?

Customary units of weight refer to the systems of units historically used in the United States, United Kingdom, and other English-speaking countries to measure weight. The most common customary units for weight are pounds, ounces, tons, and grains.

## The Pound

The pound is the most widely used customary unit for measuring weight. One pound is equal to 16 ounces. Some key facts about the pound:

• Abbreviated as “lb” or sometimes “#”
• Originally based on the average weight of a specific amount of grain or water
• Used to measure the weight of food items, animals, commercial goods, and more
• 1 pound = 16 ounces
• Common fractions of a pound include half pound (8 oz) and quarter pound (4 oz)

### Origins of the Pound

The pound originated from the Roman unit of weight known as the “libra.” The exact origins are uncertain, but some sources suggest the libra was based on the weight of a specific amount of grain or the weight of a defined amount of water. Over time, various definitions were used in different parts of Europe. Today, the most widely used definition is the International Pound, equal to exactly 0.45359237 kilograms.

## The Ounce

The ounce is primarily used as a unit of weight in both the US customary system as well as the British imperial system. Some key facts about the ounce:

• Abbreviated as “oz”
• 1 ounce = 28.3495 grams
• 16 ounces = 1 pound
• Typically used for weighing small items
• Common uses include food, cooking, metals, and postal rates

### The Troy Ounce

There are actually two different systems for the ounce. In addition to the standard avoirdupois ounce, there is also the troy ounce, primarily used to weigh precious metals such as gold, silver, and platinum. One troy ounce is equal to 31.1034768 grams.

## The Ton

The ton represents a much larger unit of weight in the customary system equal to 2,000 pounds. Some key facts about the ton:

• The short ton is the most common definition used in the US
• 1 short ton = 2,000 lbs
• Used to measure weight in large quantities – vehicles, heavy goods, materials, etc.
• 1 metric ton = 1,000 kg = 2,204.62 pounds
• Alternative spellings include “tonne” and “metric ton”

### Types of Tons

There are several different types of tons used in different contexts:

Ton Definition
Short ton 2,000 pounds
Long ton 2,240 pounds
Metric ton 1,000 kilograms or 2,204.62 pounds
Tonnage Refers to the weight capacity of a vehicle

## Grains

The grain is a small unit of weight equivalent to just 64.79891 milligrams. While not commonly used today, grains were historically important for precise measurements:

• Mainly used to weigh gunpowder and bullets
• Important in pharmacy for weighing medicine
• Originally based on the weight of a single grain of wheat or barley
• 7,000 grains = 1 pound
• Shorthand “gr”

### The Pennyweight

Another obsolete unit of weight tied to the grain is the pennyweight. It was equal to 24 grains or about 1.55517384 grams. Pennyweights were mainly used to weigh silver and other precious metals.

## Conclusion

In summary, the main customary units of weight include the pound, ounce, ton, and grain. The pound and ounce are still widely used in day-to-day contexts for measuring food, goods, and other consumer items. The ton represents a much heavier unit, suitable for large vehicles, materials, and cargo. And the tiny grain was important historically for precise measurement but has been replaced by the gram and milligram in most modern applications. While these customary units have largely been replaced by the metric system, they are still in common use today in many English-speaking countries.