# Metric System (System Internationale)

The metric system, often referred to as SI (System Internationale), is a decimal system with units that are logically related; it is widely used around the world, and in science and manufacturing.

#### Basic Units

• gram – (mass/weight) originally, the weight of a cube of water holding 1/100 meter or 1 cubic centimeter (cm3), or about 1/28 ounce (1 ounce = about 28.35 grams)
kilogram = 1,000 grams, or approximately 2.2 pounds
• liter | litre – (volume) = 1,000 cubic centimeters (cm3), or approximately 1.75 pints
• meter | metre – length , or approximately 39.37 inches   (originally based on the length of a pendulum with a period of 1 second)

Other common base units:

• are – 100 square meters (1/100 of a square kilometer)
hectare = 10,000 square meters, or about 2.47 acres
• degree (°) – temperature using Celsius / centigrade scale. 1°C=1.8°F; the zero point for the Celsius system is the freezing point of water, or 32°F
[°C = °F -32 * 5/9; °F = °C * 9/5 + 32]
• joule (J) – energy (107 erg)
• Newton (N) – force
• Pascal (Pa) – pressure
• second – time
• Watt (W) – power (amperes * volts)

In the metric system, larger and smaller units are designated by prefixes; here are some of the most common:

• pico (p)– 1 trillionth, 10–12
• nano (n)– 1 billionth, 10–9
• micro (µ) – 1 millionth, 10–6
• milli (m) – 1 thousandth, 10–3
• centi (c) – 1 hundredth, 10–2
• deci (d) – 1 tenth, 10–1

• deca (da) – ten (101)
• hector (h) – 100 (102)
• kilo (k) – 1,000 (103)
• mega (M) – million (106)
• giga (G) – billion (109)
• tera (T) – trillion (1012)

You can obtain a free set of metric education resources for use in your classroom! Contact the NIST Metric Program at TheSI@nist.gov and include your name, school, subject, grade level, phone number, and mailing address. The NIST SI Teacher Kit contains a classroom set of metric rulers (NIST SP 376 – a 300 mm ruler), laminated metric conversion cards (NIST SP 365), SI Education CD, and other measurement resources.

### Additional  Resources  on  the  Metric  System

Also see Resources that apply to many subject areas and Readings for students.