Summary
| Subject keyword(s) | Mathematics, Measurement, Number and operations, Physical measurements, Science, Science -- General science, Systems of measurement, Units, Units -- Dictionaries., Weights and measures |
|---|---|
| Grade level | Middle School, High School, Higher Education, Informal Education, Vocational/Professional Development Education |
| Intended audience | Educator, General Public, Learner, Professional/Practitioner |
| Resource type | Instructional Material, Reference Material |
| Resource format | text, text/html |
| Rights | Russ Rowlett and the University of North Carolina at Chapel Hill |
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Content contained within the resource
How Many? A Dictionary of Units of Measurement For information on a specific unit, click on the first letter of its name: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Answers to the three most frequently asked questions: How many micrograms (µg, ug or mcg) in a milligram (mg)? 1000 micrograms = 1 milligram, and 1000 milligrams = 1 gram. How can I convert from international units (IU) to milligrams or micrograms? Generally speaking, you can't. IU's measure the potency of a drug, not its mass or weight. What countries besides the U.S. have not adopted the metric system? Many U.S. teachers think the answer is "Liberia and Burma" (make that Myanmar). Let's give Liberia and Myanmar a break! All countries have adopted the metric system, including the U.S., and most countries (but not the U.S.) have taken steps to eliminate most uses of traditional measurements. However, in nearly all countries people still use traditional units sometimes, at least in colloquial expressions. Becoming metric is not a one-time event that has either happened or not. It is a process that happens over time. Every country is somewhere in this process of going metric, some much further along than others. Commentary and Explanation Using the Dictionary Using Numbers and Units Roman and Arabic Numerals Names of Large Numbers Symbols and Abbreviations The International System (SI) SI Base (Fundamental) Units SI Derived Units Metric Prefixes SI Units for Clinical Data in Medicine The English Customary Systems The Metric System CGS and MKS Units Spelling of Metric Units The Metric System in the United States ISO and IOC country codes Links to Related Sites Bibliography What's New the kilowatt year, an energy unit Dvorak T-numbers to measure tropical cyclones the ream as an area measure for film or paperboard Index of Tables and Scales Apgar scoring (newborns) Beaufort scales (wind velocity) Bushel weights (U.S.) Cotton bale weights Danjon scale (lunar eclipse brightness) Drought severity (U.S.) Fujita scale (tornados, U.S.) Glasgow coma scale Grit sizes Hat sizes Mercalli scale (earthquakes) Nutritional daily values (U.S.) Paper sheet sizes (ISO) Paper sheet sizes (traditional) Paper sheet sizes (U.S. basic sizes) Radiocarbon year conversion Saffir-Simpson scale (hurricanes, U.S.) Sheet metal gauges Shot pellet sizes Shotgun gauges SI units for medical data Solar flare intensity Tennis racquet gauges Torino impact hazard scale Tropical cyclone categories (Australia) Viscosity grades (ISO) Volcanic Explosivity Index Wind chill chart (U.S.) Wire gauge table (U.S./U.K.) Introduction Americans probably use a greater variety of units of measurementthan anyone else in the world. Caught in a slow-moving transitionfrom customary to metric units, we employ a fascinating and sometimesfrustrating mixture of units in talking about the same things. Wemeasure the length of a race in meters, but the length of the longjump event in feet and inches. We speak of an engine's power inhorsepower and its displacement in liters. In the same dispatch, wedescribe a hurricane's wind speed in knots and its central pressurein millibars. Furthermore, our English customary unitsdo not form a consistent system. Reflecting their diverse roots inCeltic, Roman, Saxon, and Norse cultures, they are often confusingand contradictory. There are two systems for land measurement (onebased on the yard and the other on the rod) and a third system fordistances at sea. There are two systems (avoirdupois and troy) forsmall weights and two more (based on the long and short tons) forlarge weights. Americans use two systems for volumes (one for drycommodities and one for liquids) and the British use a third (BritishImperial Measure). Meanwhile, only a few Americans know that the legal definitions ofthe English customary units are actually based on metric units. TheU. S. and British governments have agreed that a yard equals exactly0.9144 meter and an avoirdupois pound equals exactly 0.453 592 37kilograms. In this way, all the units of measurement Americans useevery day are based on the standards of the metricsystem. Since 1875, in fact, the United States has subscribed tothe International System of Weights andMeasures, the official version of the metric system. This dictionary began as a collection of notes describing therelationship between various English and metric units. It graduallygrew until it finally became too large a word-processing document; Icouldn't find my way around in it any more. So I turned it into afolder of html documents and added it to my Internet site. For manymonths, no one looked at the site except me and my students. Then,gradually, the dictionary began to attract users from around theworld. Many users were kind enough to point out errors; otherssuggested additions and improvements. Questions about units began toappear in my email inbox. Sometimes I could answer the questions,sometimes not. Today the dictionary has become a kind of interactive resource. Itgrows slowly and steadily, mostly through suggestions from readersand my efforts to answer questions posed by readers. You canparticipate in this process! Pleaselet me know if you find any errors on the site, or if you can'tfind what you wanted to know, or if you know of units used in yourfield of study or in your part of the world that aren't included. I hope you find the dictionary useful and informative. Formalities Written by: Russ Rowlett, Director, Center for Mathematics and Science Education University of North Carolina at Chapel Hill. You are welcome to emailthe author (rowlett@email.unc.edu) with comments andsuggestions. All material in this folder is copyright © 2005 by Russ Rowlett and the University of North Carolina at Chapel Hill. Permission is granted for personal use and for use by individual teachers in conducting their own classes. All other rights reserved. You are welcome to make links to this or any page of the dictionary. Please do not copy the contents of any page of the dictionary to another site. The material at this site is updated frequently as new information is added, so linking to the site rather than copying it is in the best interests of everyone. The information contained in the dictionary is as accurate as I can make it; please notify me if you find any errors. Neither the author nor the University of North Carolina assumes any liability for uses made of the information presented by this web site. The dictionary is not designed to promote any system of measurement. Its only purpose is to present information useful to anyone interested in the subject. July 11, 2005