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
- Education Resources on the Metric System (SI). National Institute of Standards & Technology website.
- Math Is Fun – Metric System of Measurement. Math is Fun website.
- Metric Chocolate Chip Cookies. National Institute of Standards & Technology website.
- Metric Recipes and Recipe Conversion. The Metric Kitchen website.
- The Metric System, the U.S.A., and Scientific Literacy. Public Library of Science website.
- Everyday Use of Metric. Think Metric website. Created for the U.K., but has useful information.
- Every Day With Metric. National Institute of Standards & Technology website.