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 pound
  • 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)
Common Prefixes

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