United States customary units facts for kids

The U.S. customary units are the main way people measure things in the United States. This system is quite similar to the Imperial units used in some other countries, and sometimes they are exactly the same!

Imagine you want to measure how long something is. You might use inches, feet, yards, or miles. If you're talking about land, you'd use square miles or acres.

For liquids, there are many units like the teaspoon, tablespoon (which is 3 teaspoons), fluid ounce (2 tablespoons), cup (8 ounces), pint (2 cups), quart (2 pints), and the US gallon (4 quarts). When measuring oil, people often use a unit called a barrel.

Temperature in the U.S. is usually measured in degrees Fahrenheit (°F). If you know the temperature in °C, you can change it to Fahrenheit using a simple math rule: multiply the Celsius temperature by 9/5, then add 32.

When you want to know how heavy something is, you'd use units of weight and mass. The main unit is the pound (about 453.6 grams), which has 16 ounces. It's important not to mix this up with the British pound, which is a type of money! The word "pound" can be confusing because it means different things. There are also different sizes of ounces.

For a long time, since the 1820s, some people have tried to switch the U.S. to the metric system. Many old buildings and roads in the U.S. were built using the older measurements. In the 1900s, some areas like science, medicine, and the military of the United States started using the metric system. However, most Americans still use the old units for everyday things. But around the world, almost everyone else uses the metric system, especially for global trade.

How Do We Measure Length?

When you want to know how long something is, you use units of length. Here are some common U.S. customary units for length and how they compare to the metric system:

• 1 inch (in) is about 2.54 centimeters (cm).
• 1 foot (ft) is 12 inches, which is about 30.48 cm.
• 1 yard (yd) is 3 feet, or about 0.9144 meters (m).
• 1 mile (mi) is 1,760 yards, which is about 1.609344 kilometers (km).

There are also smaller units used in printing:

• 1 point (p) is about 0.4 millimeters (mm).
• 1 pica (P̸) is 12 points, or about 4.2 mm.

How Do We Measure Area?

Area tells you how much surface something covers. Here are some U.S. customary units for area:

• 1 square foot (sq ft or ft²) is about 0.0929 square meters (m²).
• 1 acre is a common unit for land. It's equal to 4,047 square meters (m²).
• 1 section is a much larger area, equal to 640 acres, or about 2.6 square kilometers (km²).
• 1 (survey) township (twp) is 36 sections, which is about 93.2 km².

How Do We Measure Volume?

Volume tells you how much space something takes up. This can be for solids, liquids, or dry goods.

Measuring Liquid Volume

These units are used for liquids like water or juice:

• 1 teaspoon (tsp) is about 4.92892 milliliters (mL).
• 1 tablespoon (Tbsp) is 3 teaspoons, or about 14.7868 mL.
• 1 US fluid ounce (fl oz) is 2 tablespoons, or about 29.5735 mL.
• 1 US cup (cp) is 8 fluid ounces, or about 240 mL.
• 1 (liquid) US pint (pt) is 2 cups, or about 473.176 mL.
• 1 (liquid) US quart (qt) is 2 pints, or about 0.946353 liters (L).
• 1 (liquid) US gallon (gal) is 4 quarts, or about 3.78541 L.
• 1 oil barrel (bbl) is a special unit for oil, equal to 42 gallons, or about 158.987 L.

Measuring Dry Volume

These units are used for things like grains or fruits:

• 1 (dry) pint (pt) is about 0.6 L.
• 1 (dry) quart (qt) is 2 dry pints, or about 1.1 L.
• 1 (dry) gallon (gal) is 4 dry quarts, or about 4.4 L.
• 1 bushel (bu) is 4 gallons, or about 35 L.

How Do We Measure Weight and Mass?

Weight and mass tell you how much "stuff" is in something.

Avoirdupois Weight

This is the most common system for everyday items:

• 1 ounce (oz) is about 28.3495 grams (g).
• 1 pound (lb) is 16 ounces, or about 453.592 g.
• 1 short ton is 2,000 pounds, or about 907.185 kilograms (kg).

Troy Weight

This system is used for measuring precious metals like gold and silver:

• 1 troy ounce (oz t) is about 31.1035 g. Notice this is slightly heavier than a regular ounce!
• 1 troy pound (lb t) is 12 troy ounces, or about 373.242 g.

Images for kids

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  A shampoo bottle showing both U.S. and metric measurements.

Related pages

• Different ways to measure things

See also

In Spanish: Unidades tradicionales de Estados Unidos para niños