Customary units of measurement are the traditional units used in the United States to measure quantities like length, volume, and weight. They consist of units like inches, feet, yards, ounces, pounds, gallons, etc. These units originated in Britain and were brought over to the American colonies in the late 18th century. Over time, they became established as the standard system of measurement in the U.S. The key customary units used today include:
Length
- Inch – The inch is the basic unit of length in the customary system. One inch is defined as exactly 2.54 centimeters.
- Foot – A foot is equal to 12 inches. This unit is commonly used to measure a person’s height as well as short distances.
- Yard – A yard is defined as 36 inches or 3 feet. It is used to measure medium-range distances.
- Mile – A mile is equal to 5,280 feet or 1,760 yards. It measures long distances like those between cities.
Volume
- Fluid Ounce – A fluid ounce is used to measure the volume of liquids. 1 fluid ounce = 29.57 milliliters.
- Cup – A cup is equal to 8 fluid ounces or 0.5 pints. It is used for measuring ingredients while cooking and baking.
- Pint – A pint equals 16 fluid ounces or 2 cups. It is commonly used to measure amounts of milk or beer.
- Quart – A quart is 32 fluid ounces or 2 pints. It is used to measure larger volumes of liquids.
- Gallon – A gallon contains 128 fluid ounces or 4 quarts. It measures large amounts like those for gasoline or paint.
Weight
- Ounce – An ounce is the basic unit of weight in the customary system. One ounce is equal to 28.35 grams.
- Pound – A pound is 16 ounces. This is widely used to state a person’s weight or the weight of groceries, mail, etc.
- Ton – A ton equals 2,000 pounds. It measures very heavy weights like those of cargo, trucks, etc.
In addition to these basic units, there are many other customary units that are derived from them like cubic inches, square feet, cubic feet, etc. for measuring volumes. Understanding these units is essential for daily activities like cooking, traveling distances, buying produce, constructing buildings and more in the United States.
Origins and History
The origins of the customary system date back to medieval England. During the Middle Ages, a system of weights and measures started emerging based on natural references. For instance, a foot was considered equal to the length of a man’s foot while an inch equaled the width of a thumb. similarly, a yard corresponded to the distance between a man’s nose and the end of his outstretched arm. Units for volume like cups, pints and gallons were also derived from common containers used at that time.
Over the centuries, these units were standardized by kings and governments to enable trade and commerce. It was not until the 13th century, that King Henry III formalized many of these units of weights and measures as standards. The English standards continued evolving with time and spread with colonization to places like America.
In the eighteenth century, each of the American colonies had their own set of measurement standards for regulating local commerce. These were similar to British units but had key differences. For example, the American gallon was based on the wine gallon established by Queen Anne in 1707 which was different from the ale gallon used in England.
After independence in 1776, the U.S. Constitution gave Congress the power to “fix the Standard of Weights and Measures”. Efforts were made to harmonize the separate measurement systems across the country. In 1832, the U.S. Customary System was formally adopted defining the inch, yard, and pound as the primary standards which were close approximations of the British Imperial units. From then on, the customary system became entrenched in the U.S. for all practical uses despite metrication efforts in the late 19th century. It continues to be widely used today in day to day activities by both individuals and businesses.
Advantages
The customary system became popular in the U.S. because it provided some key benefits:
Familiarity
The units like feet, pounds, quarts, etc. were already familiar to most Americans by the 19th century. Retaining them avoided the trouble of transitioning to unfamiliar metric units.
Human Scale
Many customary units are based on parts of the human body and can be easily visualized. For instance, an inch is about the width of a thumb, while a foot is the length of a shoe. This makes them intuitive.
Fractions
Customary units allow fractions which make them easy for use in construction, cooking, etc. One can precisely measure 3/4th yards of cloth or 1/2 cup of milk. Decimals don’t work as well for such scenarios.
Lessdecimals
The customary system typically involves fewer decimals compared to metric which simplifies measurements for the layman. For example, a person’s height is 6 feet 1 inch rather than 1.85 meters.
Overall, the customary system was well adapted for use by everyday people in their daily lives rather than just scientists. Its entrenchment in American society for over two centuries has made it difficult to displace.
Disadvantages
Despite its utility, the customary system also has some notable drawbacks:
Complex conversions
There are no simple conversion ratios between the units. Converting between units like inches, feet, yards, and miles requires recalling random conversion factors. This makes it cumbersome to switch between units.
Non-standard prefixes
Unlike the metric system with its standard SI prefixes like kilo, milli, micro, etc. the customary system has no systematic way to scale units up and down. Units like pounds, tons, ounces, grains, etc. have no logical relationship.
Non-base 10
The customary system is not decimal-based. Units like 12 inches = 1 foot, 3 feet = 1 yard, 22 yards = 1 chain do not scale up by factors of 10. This adds complexity compared to the metric system.
Not aligned to modern science
Modern science relies on the metric system. Using a different system like customary units hampers easy conversion for applications in science, engineering, medicine and more. It creates extra work to convert between the two systems.
Due to these factors, most nations have now standardized on the metric system. The United States remains one of the few countries still using customary units, leading to some challenges in international commerce and scientific research.
Common Customary Units
Here is a more detailed look at some of the frequently used customary units:
Length Units
| Unit | Abbreviation | Conversion |
|---|---|---|
| Inch | in | 1 in = 2.54 cm |
| Foot | ft | 1 ft = 12 in |
| Yard | yd | 1 yd = 3 ft = 36 in |
| Mile | mi | 1 mi = 1,760 yd = 5,280 ft |
Volume Units
| Unit | Abbreviation | Conversion |
|---|---|---|
| Fluid Ounce | fl oz | 1 fl oz = 29.57 ml |
| Cup | c | 1 c = 8 fl oz |
| Pint | pt | 1 pt = 2 c = 16 fl oz |
| Quart | qt | 1 qt = 2 pt = 4 c |
| Gallon | gal | 1 gal = 4 qt = 8 pt = 16 c |
Weight Units
| Unit | Abbreviation | Conversion |
|---|---|---|
| Ounce | oz | 1 oz = 28.35 g |
| Pound | lb | 1 lb = 16 oz |
| Ton | tn | 1 tn = 2,000 lb |
In addition, some other units like dram, grain, minim, rod, furlong, league, knot etc. were historically used but are now obsolete. The units listed above are the most relevant for everyday use.
Converting Between Customary and Metric Units
Since the customary and metric systems are completely independent, converting between them requires memorizing key conversion factors:
Length
- 1 inch = 2.54 cm
- 1 foot = 30.48 cm
- 1 yard = 0.9144 m
- 1 mile = 1.609 km
Volume
- 1 fl oz = 29.57 ml
- 1 pint = 473.18 ml
- 1 quart = 0.946 liters
- 1 gallon = 3.785 liters
Weight
- 1 ounce = 28.35 g
- 1 pound = 453.59 g
- 1 short ton = 907.185 kg
Converting larger units is done by first converting the units into smaller ones like inches, ounces etc. and then using the basic conversions. For example, to convert 10 miles to km, first convert miles to inches, then inches to cm, and finally cm to km.
While these conversions have been standardized, slight variations exist depending on the definitions used historically. Caution should be exercised when accuracy is vital.
Daily Use Cases
Despite metrication efforts, customary units remain in widespread daily use across the United States. Some examples include:
Cooking
Recipes typically use cups, teaspoons, tablespoons, fluid ounces, and other volume measures along with pounds and ounces for weight.
Weather Forecasts
Weather forecasts report temperature in degrees Fahrenheit and rainfall amounts in inches. Only scientific contexts use Celsius and mm.
Human Height and Weight
A person’s height is stated in feet and inches while weight is measured in pounds. Baby weights are sometimes still in ounces.
Retail and Grocery Shopping
Packaged goods sold in stores display volumes in fluid ounces, pounds, item dimensions in inches etc. Prices are also usually in dollars and cents.
Driving Distances
Road signs and trip planning uses miles to denote distances. Vehicle speed is measured in miles per hour (mph). Gas fuel efficiency is miles per gallon (mpg).
Construction
Buildings, materials, furniture and more are designed using inches, feet and yards for key dimensions and areas. Pipes sizes are in inches.
Sports
Many American sports use yards (football), feet (golf), miles (running races), ounces (boxing) and other customary units for measurements.
So customary units remain deeply ingrained in the everyday lives of people due to long familiarity. Businesses also continue supporting such units on packaging and advertising to appeal to their customers. Scientific and international contexts are the only places where metric units dominate in the country.
Efforts to Transition to Metric System
The global standardization of the metric system has led to periodic efforts to increase its use in place of customary units in the United States:
19th Century
In the early 19th century, the metric system was looked upon favorably by political leaders like John Quincy Adams who wanted to align with the French decimal-based system. The ‘Mendenhall Order’ in 1893 made metric standards official for the country. However, general public opinion remained opposed to displacing the familiar customary units.
1970s
In the 1970s, rising world trade provided an impetus for metrication. The Metric Conversion Act of 1975 started a decade long transitionary period towards the system. Voluntary metric usage saw an uptick in sectors like automobile, healthcare, military, etc. But again lack of public enthusiasm stalled large scale conversion.
1980s – Onwards
Throughout the ’80s and beyond, various industries voluntarily adopted metrics – examples being photographic lenses, beverages, ammunition, digital devices and more. But large parts of American life like retail, construction, recipes etc continue using customary units as before.
Overall, the piecemeal transition towards metrics has slowed and stalled over the past few decades. With no major public inconvenience caused by traditional units, a full-scale shift seems unlikely unless the Federal government mandates it through legislation in the future. But this remains politically controversial.
Conclusion
Customary units are deeply ingrained in the American tradition due to their origins from medieval England and early adoption following independence. Despite clear disadvantages compared to the metric system, their familiarity in daily use cases related to human scale has ensured their continued popularity over time. Although portions of the economy like science, international trade and some industries have voluntarily adopted metrics, full metrication still remains elusive due to lack of sufficient public or political motivation. Barring major new legislation, customary units seem poised to retain their dominant status in American life for the foreseeable future.