Unit Conversion Guides

The converter gives you a number; these guides explain where it comes from. Each one covers a single unit system or topic, with reference tables, exact formulas, worked examples and answers to the questions people most often ask.

All Guides

• SI Base Units and PrefixesThe 7 SI base units and all 24 prefixes from quecto to quetta, in one table.
• SI Derived Units in Base UnitsNewton, joule, watt, coulomb, volt, ohm and all 22 named units broken down into kg, m, s and A.
• Celsius, Fahrenheit, Kelvin and RankineEvery temperature formula, a reference chart and the difference between absolute and relative scales.
• Bits, Bytes, KB vs KiBDecimal vs binary storage units, why 1 TB shows as 931 GB, and Mbps vs MB/s.
• Metric vs. ImperialWhere each system is used, exact conversion factors and how US and UK units differ.
• Cooking ConversionsCups to grams by ingredient, spoons to millilitres and an oven temperature chart.

Looking for a Quick Conversion?

For a single value, use the ConvertMe.org converter, which covers more than thirty categories, or browse the conversion index for dedicated pages such as km to miles, kg to lbs and Celsius to Fahrenheit.