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
  • quad – 1015 Btu
  • 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.