- All Measures - Conversion table of non-metric measures into SI and CGS.
- Ask Numbers - Offers a wide variety of unit conversion tools and conversion charts for fast lookup.
- British Weights and Measures Association (BWMA) - Pressure group opposing compulsory metrication. Political, consumer and transport information, discussion boards and links.
- 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.
- 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.
- 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.
- 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.
- 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.
- Metric Conversion Tables to Imperial Measurements - Standard-to-metric conversion factor tables with definitions, derived units and prefixes.
- Metric Scale - Answers the question "What do ppm, ppb, ppt and ppq stand for?". Includes illustrated examples of sizes in the metric system.
- National Measurement Office (UK) - Includes information about the National Measurement System, legislation and guidance, services to industry, and its enforcement role.
- NIST Metric Information and Conversions - Factsheets, regulations and conversion tools. Official site of the United States Metric Program.
- SI Guide - Provides translation of unit and prefix names for the international metric system (SI) into various languages. For some, transliterations are also given.
- 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.
- The Metric System - Outline of the metric system with emphasis on applications in physics.
- UK Metric Association - Pressure group campaigning for the completion of metrication in the UK. History, legislation, and practical help.
- Units of Measurement - Conversions tables and equivalences of the principal units of measure of the SI and Anglo-Saxon systems.
