# US Standard Units|Definition & Meaning

## Definition

The **US** standard **units** refer to the **measurement** units used within the **USA**. These are related to the **metric** units (**SI** Units) but are more convenient in some cases. These units measure quantities such as **mass** (pounds, tons, etc.), **length** (miles, feet, etc.), fluid **volumes** (fluid ounces, gallons, etc.), and **temperature** (Fahrenheit).

**Figure 1** shows all the **US units** along with the physical **quantities** that they belong to.

## History

The **US** standard units were derived and adapted from the **imperial** system of weights and measures in **1832** by the US government. The imperial system was developed by the British in **1824**. Later on, in 1864, the **British** adopted the **metric** system, which was developed by French scientists in **1795**. but the **US** still uses its customary units such as pounds, ounces, feet, inches, miles, etc.

All the **US** standard units are exactly the **same** as the units of mass, length, etc., used in the **imperial** system except for the units of **volume**. The **units** used to measure the volume of **fluids** in the US system are **smaller** than their imperial counterparts. For example, **one** fluid ounce in the US system is equal to **1.0408** fluid ounces in the imperial system. Also, the **US** gallon is **20%** smaller than the **imperial** gallon.

The **US** standard units used to measure the **volume** of liquids, the **mass** of dry ingredients, **length,** and **temperature** are discussed below.

## Volume of Liquids

A liquid is a **fluid** that takes the shape of its container. It is **incompressible** and has a constant volume. It is one of the four basic states of matter, having no fixed **shape** but a definite **volume**. The volume of liquids is **measured** in the following **US** standard units.

### Fluid Ounces

The fluid ounce is the **smallest** unit to measure the **volume** of a liquid. It is abbreviated as “**fl oz**” and is also called a **regular** ounce. The **SI** volume unit is a **cubic meter** which is equal to one kiloliter (**kL**). The smaller unit milliliter (**mL**) is related to one fl oz as:

1 US **fl oz** = 29.5735 **mL**

The **US** customary fluid ounce is **4.08%** greater than the **imperial** fluid ounce. So,

1 **imp** fl oz = 0.96076 **US** fl oz

A fluid ounce is equal to **6** US **teaspoons** and **2** US **tablespoons**. One fluid **ounce** is related to the other US units of **volume** as follows:

1 US **fl oz** = 1/8 or 0.125 US **cups**

1 US **fl oz** = 1/16 or 0.0625 US **pints**

1 US **fl oz** = 1/32 or 0.03125 US **quarts**

1 US **fl oz** = 1/128 or 0.0078125 US **gallons**

### Cups

A US** cup** is equal to **eight** US **fluid ounces**. It is also equal to **8.45** imp fl oz. It is used in the measurements of **cooking** units, nutrition labeling, and **serving** sizes in the US. The US **cup** is related to the other US units of **volume** as:

1 US **cup** = 48 US **teaspoons**

1 US **cup** = 16 US **tablespoons**

1 US **cup** = 1/2 or 0.5 US **pints**

1 US **cup** = 1/4 or 0.25 US **quarts**

1 US **cup** = 1/16 or 0.0625 US **gallons**

Also:

1 US **cup** = 236.588 **mL**

### Pints

One US **fluid** pint is equal to sixteen US liquid **ounces**. Also,

1 US **pint** = 568.261 **mL**

One US **pint** is related to the other **units** of liquid **volume** as:

1 US **pint** = 2 US **cups**

1 US **pint** = 1/2 or 0.5 US **quarts**

1 US **pint** = 1/8 or 0.125 US **gallons**

### Quarts

One quart refers to the **quarter** or one-fourth of a **gallon**. One quart is equal to **946.353 mL**. A quart can be converted to any other **US unit** by using the following unit **conversion**:

1 US **quart** = 32 US **fl oz**

1 US **quart** = 4 US **cups**

1 US **quart** = 2 US **pints**

1 US **quart** = 1/4 or 0.25 US **gallons**

### Gallons

One gallon is equal to **3785.41 mL**. It is the **largest** US unit of volume. For example, a water **truck** can carry approximately **9000** gallons of **water**.

**Figure 2** shows a summary of **conversions** of all the **US** standard units of **liquids**.

## Mass

Mass is the amount of **matter** composed within an **object**. Mass is often confused with **weight**. Weight is the mass of the object due to **gravitational** pull. The following **US** units are used for the **mass** of an object.

### Ounces

Ounces are **different** from **fluid** ounces. It is the **smallest** US unit of mass and is abbreviated as “**oz**.” It is related to the other US units of **mass** as follows:

1 **oz** = 1/16 or 0.0625 **lb**

1 **oz** = 1/32,000 **tons**

### Pounds

A pound is also known as the “**pound-mass**” and is abbreviated as “**lb**.” One pound is equal to **sixteen** ounces. Also,

1 US **lb** = 1/2000 US **tons**

Pounds are the main **unit** to measure the **weight** of a person, animal, or object.

### Tons

A ton, abbreviated as “**t,**” is the **largest** unit of mass. One ton is equal to **2000** pounds. Also,

1 US **ton** = 32,000 **oz**

For example, a **truck** has a mass of **3 tons**.

**Figure 3** shows the **US** unit conversions of **mass** and the US units in the **SI** unit of mass, i.e., **kilogram**.

## Length

The measure of **distance** is known as length. It serves as a **base** unit in many **systems** of measurements from which many other units are **derived**. The **metric** unit of length in **meters**. The following **US** units are used to measure the length.

### Inches

An inch is the **smallest** unit of length, abbreviated as “**in**.” It is related to the other **US** units of **length** as follows:

1 **inch** = 1/12 **feet**

1 inch = 1/36 **yards**

1 inch = 1/63,360 **miles**

For example, the **length** of a piece of **paper** can be measured in **inches**.

Also,

1 **m** = 39.3701 **inches**

### Feet

One **foot, **abbreviated as **“ft,”** is equal to **12** inches. Also,

1 **ft** = 1/3 **yards**

1 ft = 1/5280 **miles**

For example, a **car** is about** 14.7 feet** long. Also,

1 **m** = 3.28084 **ft**

### Yards

A yard is equal to **3 feet**. For **example**, the length of a **bed** is about **2** yards. Also,

1 **yard** = 36 **inches**

1 yard = 1/1760 **miles**

One **yard** is equal to **0.9144 m**.

### Miles

One mile is equivalent to **1760** **yards**. This **large** unit of length is usually used to measure long **distances** between different **places**. For example, it takes **189 **miles to travel from Rawalpindi to Lahore. Also,

1 **mile** = 63,360 **inches**

1 mile = 5280 **ft**

One **mile** equals **1609.34** **meters**.

**Figure 4** shows all the **US** units of **length** converted from one unit to another.

## Temperature

A temperature measures the extent of **hotness** and coldness in a **quantifiable** way. It is measured by a thermometer which has some **thermometric** substance and a reference point calibrated with a certain temperature **scale**.

The **temperature** can be measured in degrees of **Celsius**, Fahrenheit, and Kelvin. The **US** unit of temperature is **Fahrenheit,** and its** SI** unit is **Kelvin**.

### Fahrenheit

To convert **Celsius**(°C) to **Fahrenheit**(°F) scale, multiply the temperature by **9/5** or **1.8**, and add **32**. For example, 35 °C is **converted** to Fahrenheit scale as follows:

35 **°C** = ( 35 ✕ 1.8 ) + 32 **°F**= **95 °F**

To convert **Kelvin**(K) to degree **Celsius**, subtract **273.17** from the Kelvin temperature. For example, to convert **500 K** into Celsius:

500 K = 500 – 273.15 °C = **226.85 °C**

## Examples

### Example 1 – US Unit Conversion for Liquids

Convert** 52** cups into **quarts**.

#### Solution

As:

**1 cup = 0.25 quarts**

52 cups = 52 × 0.25 quarts

52 cups = 13 quarts

Hence, **52** US cups are equal to **13** US **quarts**.

### Example 2 – US Unit Conversion for Mass

Convert **8000** pounds into **tons**.

#### Solution

As:

**1 lb = 1/2000 tons**

8000 lb = 8000 × 1/2000

8000 lb = 4 tons

Hence, **8000** pounds are equal to **4 tons**.

### Example 3 – US Unit Conversion for Length

Convert **5000** miles into **yards**.

#### Solution

As:

**1 mile = 1760 yards**

5000 miles = 5000 × 1760 yards

5000 miles = 8,800,000 yards

Therefore, **5000** miles equals **8,800,000** yards.

### Example 4 – US Unit Conversion for Temperature

Convert **450** Kelvins into **Fahrenheit**.

#### Solution

First, **450 K** is converted in the **Celsius** scale as:

450 K = 450 – 273.15 °C

450 K = 176.85 °C

Then, **176.85 °C** is converted in degrees **Fahrenheit** as:

176.85 °C = (176.85 °C × 1.8) + 32 °F

176.85 °C = 318.33 + 32 °F = 350.33 °F

Therefore, **450 K** is equal to **350.33 °F**.

*All the images are created using GeoGebra.*