# Measurements

## Converting English Measurements

Here are some conversions that you should know in the English system:

### Length

1 foot = 12 inches
1 yard = 3 feet
1 mile = 5280 feet
1 gallon = 16 cups
1 gallon = 4 quarts

### Mass

1 pound = 16 ounces
1 ton (in United States) = 2000 pounds

## The Metric System

Metric system is based on the SI (Système International d'Unités) units.

### Length

Length is measured in meters (m). There are 100 centimeters (cm) in 1 meter, and 10 millimeters (mm) in each centimeter. Therefore, there are 1000 millimeters in each meter. There are 1000 meters in each kilometer (km).

### Mass

Mass is measured in kilograms (kg). The kilogram was originally defined as the mass of one liter of pure water at a temperature of 4 degrees Celsius and standard atmospheric pressure.

### Time

Time is measured in seconds (s). Second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium-133 atom at zero kelvins. There are 60 seconds in a minute, 3600 seconds in an hour (or 60 minutes), and 86,400 seconds in a day (or 24 hours, or 1,440 minutes). There are 1000 milliseconds in a second.

### Temperature

Temperature is measured in Kelvins or degrees Celsius (°C) in SI; the latter is used more frequently in general applications. The degree Celsius is a unit of temperature named after the Swedish astronomer Anders Celsius (1701–1744), who first proposed a similar system in 1742. The Celsius temperature scale was designed so that the freezing point of water is 0 degrees Celsius, and the boiling point is 100 degrees Celsius at standard atmospheric pressure.

### Volume

Volume is measured cubic meter (m3). The volume of a solid object is a numerical value given to describe the three-dimensional concept of how much space it occupies. One-dimensional objects (such as lines) and two-dimensional objects (such as squares) are assigned zero volume in the three-dimensional space. Liter (L and l) is used commonly. 1000 L makes a cubic meter and 1 L is 1 dm³.

## Metric Length Measurement Conversions

1 meter = 10 decimeters = 100 centimeters = 1000 millimeters
1 decimeter = 10 centimeters = 100 millimeters
1 centimeter = 10 millimeters
1 kilometer = 1000 meters = 10,000 decimeters = 100,000 centimeters = 1,000,000 millimeters
1 kilogram = 1000 grams = 1,000,000 milligrams
1 gram = 1000 milligrams

## Converting English and Metric Measurements

To convert between one measurement unit and another, requires a conversion factor. For instance;

1 inch = 2.54 cm or 25.4mm

and so 12 inches = 12 x 25.4 = 304.8mm

The same conversion factor can also be used to convert mm to inches by using division. For example;

400mm = 400/25.4 = 15.75 inches (to 2 decimal places)