Units of Measurement

All Measures
Conversion table of non-metric measures into SI and CGS.
http://www.allmeasures.com/

Allchin Measurements Converter
Converts common measurements from metric to imperial and vice versa, with other systems included for selected quantities such as light years, picas, and Old Russian measures.
http://allchin.net/converter/

Anglo-Saxon Weights & Measures
Catalogue of traditional British units with historical notes.
http://members.aol.com/Jack%20Proot/met/spvolas.html

Body Height Weight Converter
Converts from American to metric units and vice versa.
http://www.albireo.ch/bodyconverter/

British Weights and Measures Association (BWMA)
Pressure group opposing compulsory metrication. Political, consumer and transport information, discussion boards and links.
http://www.bwmaonline.com/

Chinese Numbers
Put in a number and get the Chinese representation of that number. Also, converts from Arabic numeral back to the Chinese form.
http://www.mandarintools.com/numbers.html

Cleave Books - Specialist Calculators
Features converters for perimeter measurements of geometric figures, fractions, percentages, number bases, loan repayments, growth and decay, cost of living index, fuel consumption, flow rate, specific energy, viscocity, and heat capacity.
http://www.projects.ex.ac.uk/trol/scol/

Conversion Factors for Energy Equivalents
Physics laboratory of the National Institute of Standards and Technology (NIST) sponsors and maintains this reference resource of CODATA-recommended values of fundamental physical restraints.
http://physics.nist.gov/cuu/Constants/energy.html

Conversion Tables
More than 40 different unit conversion tables.
http://www.conversiontables.info

Conversions-R-Us
Convert units of measurements, bases, and PPT, RTF, DOC, and XLS files to HTML.
http://freegroups.net/conversion/

Convert It
Features converter tools for measurement, currency exchange, world time zones, time, finance, driving distance, Roman numerals, atmosphere, and body mass index. Also, has a basic calculator and periodic table.
http://www.convertit.com

Convert-Me
Metric, English old Russian, ancient Greek and Roman, nautical, typographical and astronomical conversions.
http://www.convert-me.com

eFunda: Units and Constants
The index page for units, fundamental constants, and currencies.
http://www.efunda.com/units/index.cfm

English Weights and Measures
History and usage of English/Imperial/customary weights and measures, with conversion factors, and pictures. Minims, drachms, pecks, bushels, rods, poles, perches, furlongs, ounces, fathoms, pints, gallons, nails, chains, chaldrons, tods, crowns, florins, groats, farthings and guineas.
http://home.clara.net/brianp/index.html

EngNet Engineering Units Converter
Online calculator provides conversions between a number of common (and not so common) units.
http://www.engnetglobal.com/tips/convert.asp

Equatorial to Galactic Converter
Convert Equatorial to Galactic Coordinates.
http://fuse.pha.jhu.edu/support/tools/eqtogal.html

The Foot Rule
Convert units from one measure to another (e.g. meters to yards, liters to gallons). A very extensive collection of units and categories. Includes usage and definitions descriptions of units and categories.
http://www.footrule.com/

GoConvert
Convert currencies and measurements.
http://www.goconvert.com/

GourmetSleuth
Conversion calculators for distance, length, area, volume weights, and temperature.
http://www.gourmetsleuth.com/general_calcs.htm

How Many?
A dictionary of units of measurement: explanations of the metric system, System Internationale (SI), English customary system, and other modern measuring systems. Plus extensive links to other measurement-related Internet resources.
http://www.unc.edu/~rowlett/units/index.html

iAgora Conversions
Converts temperature, currency, length, and mass.
http://www.iagora.com/itravel/tools/

IEER Technical Classroom
Table of conversion factors for selected units relevant to nuclear topics.
http://www.ieer.org/clssroom/unitconv.html

Interactive Unit Equivalency Table Generator
Generates an equivalency table from any engineering unit to any other.
http://www.triatek.com/TriaUtil/unitconvtable.htm

International System of Units
Definitions of SI units and SI prefixes, units outside the SI, rules and style conventions, historical context for SI units, international aspects of the SI, and unit conversions.
http://physics.nist.gov/cuu/Units/index.html

Math Connect
Provides calculations of various types including metric conversion, engineering calculations, and computing finance loan payments. Also, has list of general math formulas.
http://www.mathconnect.com

Measurement Unit Converter
Converts many units of measurement using a JavaScript 1.1 applet.
http://www.people.virginia.edu/~rmf8a/convert.html

Measurement Units Translation
Measurements converter for time, length, volume, and weight. Requires JavaScript.
http://www.convert-me.com/en/

Measuring Low Concentrations
Explains with many examples the question of "What do ppm, ppb, ppt and ppq stand for?"
http://www.cefic.org/metricscale/low_concentration.htm

MegaConverter
Resource for units, weights, measures, calculators and converters.
http://www.megaconverter.com/

Metric 4 US
A site promoting the metric system which argues why metric is better and English is worse. Provides an English-metric online calculator.
http://www.metric4us.com/

Metric Conversion Tables
Conversion factors and online calculators for metric and imperial units.
http://www.metric-conversion-tables.com/

Metric Conversion Tables to Imperial Measurements
Standard-to-metric conversion factor tables with definitions, derived units and prefixes.
http://www.simetric.co.uk/

Metric Conversions
Online calculator converts between metric, British, and American units.
http://www.sciencemadesimple.com/conversions.html

The Metric System
Outline of the metric system with emphasis on applications in physics.
http://www.essex1.com/people/speer/metric.html

Metric System Formulas
Formulas for converting imperial system into metric system. Site in both English and French.
http://www.rocler.qc.ca/dusablon/wintips/

MIT 3.091 Units Converter
A tool for engineers and others to convert from almost any set of units to any other.
http://web.mit.edu/course/3/3.091_dev/javaexamples/Hello/unit-convert.html

The Modern Metric System
Dictionary of metric units explaining the principles and history of the system.
http://metre.info/

National Weights and Measures Laboratory (UK)
Official imperial-to-metric conversion tables.
http://www.nwml.gov.uk/faqs.aspx?ID=8

NIST Metric Information and Conversions
Factsheets, regulations and conversion tools. Official site of the United States Metric Program.
http://ts.nist.gov/WeightsAndMeasures/Metric/mpo_home.cfm

Online Conversion
Offers conversion tools for length, volume, temperature, astronomical, clothing sizes, computer bytes, cooking measurements, time zones, density, energy, finance, flow rates, force frequency, and some fun pages.
http://www.onlineconversion.com/

Online Converters
Provide online javascript converters and calculators for converting metric to imperial units and vice-versa.
http://onlineconverters.com

On-Line Measures Converter
Length, area, mass and weight, volume and capacity, temperature, angles, force, torque, electricals, cloth sizes, and some others.
http://amedvedev.chat.ru/

Ron's Hard Conversion Tools
Online unit conversion calculators for volume, distance, weight, and temperature units. Also includes number conversion (decimal, hex, and binary) and a tool to convert characters to or from ASCII codes.
http://www.ronshardwebapps.com/conversions.asp

The Scale of Things
Illustrated examples of sizes in the metric system, from ters- to pico-.
http://www.cefic.org/metricscale/scale.htm

SI Guide
Provides translation of unit and prefix names for the international metric system (SI) into various languages. For some, transliterations are also given.
http://www.metricmethods.com/SIguidelines.html

SI Units
Reference information on the International System of Units (SI).
http://www.chemie.fu-berlin.de/chemistry/general/si_en.html

Temperature Converter
Simple Celsius-Fahrenheit conversions.
http://www.ausmaps.com/converter.php

Temperature Converter
Converts Fahrenheit to Celsius and vice versa.
http://www.albireo.ch/temperatureconverter/

UK Metric Association
Pressure group campaigning for the completion of metrication in the UK. History, legislation, and practical help.
http://www.ukma.org.uk/

Unit Conversion and Day of the Week
Converts such things as inches to centimetres, gallon to cubic metres or even curie to becquerel
http://scphillips.com/units//index.html

Unit conversion and Reference Tables
Features converters for physical constants, SI units, temperature, currency, and temperature.
http://www.chemie.fu-berlin.de/chemistry/general/index_en.html

Unit Conversions
Online conversions from physics units to other physics units. Includes a comprehensive set of units with definitions.
http://www.chemie.de/tools/units.php3?language=e

Unit Converters
Features conversion calculators for atmospheric pressure, volume, distance, weight, velocity, temperature, and force.
http://www.scorpiosite69.freeserve.co.uk/conversions.htm

Units of Measurement
Conversions and equivalences of the principal units of measure of the SI and Anglo-Saxon systems.
http://www.themeter.net/index_e.htm

World Wide Metric
Java metric conversion calculator for length, weight, pressure, and volume.
http://www.worldwidemetric.com/metcal.htm

WWW Unit Converter
Converts area, density, energy, force, length, mass, power, pressure, speed, temperature and volume, bits and bytes.
http://www.digitaldutch.com/unitconverter/