Standard Units of Measurement Reference

• Online Calculators

• Science: Technology: Metrology 
• Reference: Time 

• British Weights and Measures Association  - Advocacy group promoting British weights and measures instead of using a compulsory use of metric system.
• Convert.net  - Online conversions calculator for a variety of unit measurements featuring natural language queries.
• English Weights and Measures  - Information on Imperial weights and measures.
• How Many?  - Offers a full dictionary of units of measurement.
• Math Connect  - Online source for metric conversions and other various types of calculations.
• Metric 4 US  - Presents arguments in favor of adopting the metric measurement system and points out the flaws or disadvantages of the English system.
• Metric Conversion Tables  - Free online resource useful in converting measurement units into their metric derivatives.
• Metric Conversion.us  - Contains a length conversion table between metric and English units.
• Metric Information and Conversions  - Presents conversion tools, metric publications, educational resources, and related news and links.
• NIST International System of Units  - Provides a reference on constants, units, and uncertainty.
• NIST Metric Information and Conversions  - Find common conversion factors such as metric to inch-pound and inch-pound to metric. Also provides conversion tools, publications and information.
• NWML: Metric Conversions  - FAQ sheet published by the UK National Weights and Measures Laboratory. Answers questions related to metric conversions and the units of measurement no longer used for trade.
• SI Metric  - Table of metric conversions with details on scientific notations and SI unit descriptions.
• Unit of Measure Conversion Equivalences  - Provides information about the international system of units (SI), SI prefixes, fundamental physical constants, and SI base and derived units.
• Universcale  - Flash site designed to allow users to experience and compare the sizes of various objects - from the smallest to the largest.