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SI units, prefixes, American equivalents of SI units

Dr. Walt Volland revised June 28, 2013

SI and Metric

There are three unit systems commonly used on a daily basis. One is the English system which uses feet, pounds, yards, etc. . Another system is the metric system (cgs) which uses centimeters, grams, seconds and relatively small units that are handy when working at a lab bench. The third system is the International System of units

A site that describes these is available here by Russ Rowlett and the University of North Carolina at Chapel Hill http://www.unc.edu/~rowlett/units/metric.html

Conversions are used for things like clothing sizes to recipes. This link shows how to do these conversions. http://www.onlineconversion.com/
SI base units and Metric units for common measureable quantities / qualities
Quality or physical property SI base unit Abbreviation Metric Abbreviation
Mass kilogram kg gram g
Length meter m meter m
Volume cubic meter m3 liter L
Time second s second s
Temperature Kelvin K Celcius oC

 

These prefixes are used in the following way.
Conversions between units
345. liters to millilters; 345 liters ( 1000 ml / 1 liter ) = 345000 ml

 

SI base units English equivalents for common measureable         quantities
Quality or physical property SI base unit Abbreviation English equivalent
Mass kilogram kg 2.205 pounds
Length meter m 3.280 feet
Volume cubic meter m3 1 M3 = 264.2 gallon
Time second s same
Temperature Kelvin K

1 oC = 1.8 oF

1 oC = 1 oK

Quality or physical property SI base unit Abbreviation Metric equivalent
Mass kilogram kg 1000 grams
Length meter m 100 centimeters
Volume cubic meter m3 1 M3 = 1,000,000 cm3
Time second s same
Temperature Kelvin K

1 oC = 1.8 oF

1 oC = 1 oK

 

SI units are large compared to the convenient sized quantities used in chemistry and the health professions. In fact the size of commonly used quanties are going down because of improved microscale technology. These smaller amounts decrease waste and side effects as well minimizing environmental impacts. Many studies have detected increased levels of prescription drugs (medications) in the environment. There are programs to collect drugs and dispose of them separately so they do not make their way into the water supply.