US Customary Units - Definition, Examples, Quiz, FAQ, Trivia
Learn about the measurement system used in the United States with easy explanations and practice activities
What are Customary Units?
Customary units are the measurement system used in the United States for everyday things. While most countries use the metric system, the US uses customary units for measuring length, weight, capacity, and temperature.
Customary units include:
- Length: Inches, feet, yards, miles
- Weight: Ounces, pounds, tons
- Capacity: Fluid ounces, cups, pints, quarts, gallons
- Temperature: Degrees Fahrenheit
Understanding these units helps us measure things accurately in daily life - from cooking to building to telling the weather!
Key Concept
Customary units are different from metric units. While metric uses multiples of 10, customary units have different conversion factors.
Customary Units of Length
We use different units to measure how long or tall something is. Here are the most common customary units for length:
Inch (in)
Smallest common unit. About the width of your thumb. 12 inches = 1 foot
Foot (ft)
About the length of an adult foot. 3 feet = 1 yard
Yard (yd)
About the length of a baseball bat. 1,760 yards = 1 mile
Mile (mi)
Used for long distances. About 4 times around a running track. 1 mile = 5,280 feet
Conversion Tip
To remember: 12 inches = 1 foot, 3 feet = 1 yard, 1,760 yards = 1 mile
Customary Units of Weight
Weight tells us how heavy something is. Here are the customary units we use:
Ounce (oz)
Lightest common unit. A slice of bread weighs about 1 ounce. 16 ounces = 1 pound
Pound (lb)
A loaf of bread weighs about 1 pound. 2,000 pounds = 1 ton
Ton (T)
Heaviest unit. A small car weighs about 1 ton. 1 ton = 2,000 pounds
Weight Tip
Remember: 16 ounces make a pound, and 2,000 pounds make a ton!
Customary Units of Capacity
Capacity units measure how much liquid a container can hold. Here are the customary units:
Fluid Ounce (fl oz)
Smallest liquid unit. A medicine cup holds about 1 fluid ounce. 8 fl oz = 1 cup
Cup (c)
A standard measuring cup. 2 cups = 1 pint
Pint (pt)
A small milk carton. 2 pints = 1 quart
Quart (qt)
A juice bottle. 4 quarts = 1 gallon
Gallon (gal)
A large milk jug. 1 gallon = 4 quarts
Capacity Tip
Remember: 2 cups = 1 pint, 2 pints = 1 quart, 4 quarts = 1 gallon
Temperature in Fahrenheit
In the US, we measure temperature in degrees Fahrenheit (°F). Here are some important temperatures to know:
Freezing point of water: 32°F
Room temperature: About 68°F
Body temperature: 98.6°F
Boiling point of water: 212°F
Fahrenheit is different from Celsius used in most countries. For example, 0°C is 32°F, and 100°C is 212°F.
Temperature Tip
Remember: Water freezes at 32°F and boils at 212°F on the Fahrenheit scale.
Converting Customary Units
Converting between customary units means changing a measurement from one unit to another. Here are the conversion factors you need to know:
Length Conversion Factors
Weight Conversion Factors
Capacity Conversion Factors
Conversion Tip
When converting to a smaller unit, multiply. When converting to a larger unit, divide.
Customary Units Practice Quiz
Test your knowledge with this 5-question quiz. Choose the correct answer for each question.
Frequently Asked Questions
Here are answers to common questions about customary units:
Measurement Trivia
Discover interesting facts about measurement systems:
Origin of the Foot
The foot as a unit of measurement dates back to ancient civilizations. The Roman foot was about 11.6 modern inches, while the Greek foot was about 12.1 inches. The modern foot (12 inches) was standardized in 1959.
Gallon Differences
There are actually two different gallons! The US liquid gallon is 3.785 liters, while the US dry gallon is 4.405 liters. The imperial gallon (used in the UK) is even larger at 4.546 liters.
NASA's Measurement Challenge
In 1999, NASA lost a $125 million Mars Climate Orbiter because one engineering team used metric units while another used US customary units for a key spacecraft operation.
Largest Measurement
The largest unit in the customary system is the league, used for measuring distance at sea. One league equals about 3 miles. The longest land measurement is the mile, with 5,280 feet.
