Volume Conversion
Metric volume measurements are based around the liter of which there are 1000 in a cubic meter (ie. 1l = 1000cm³).
Note that a US gallon is different from a UK gallon. We are not sure of the origins of a Barrel, Gallon or Pint.
Metric Weight Measurements
Metric weight units are based around the weight of respective metric volumes of water. For example, a liter of water weighs one kilogram.
Temperature Conversion
Celsius: Zero on the Celsius scale (0 °C) is now defined as the freezing point equivalent to 32° F, At 100°C the Celsius scale is defined as the boiling point and equivalent to 212° F.
Fahrenheit: Is a thermodynamic temperature scale, where the freezing point of water is 32 degrees Fahrenheit (°F) and the boiling point 212°F (at standard atmospheric pressure). This puts the boiling and freezing points of water exactly 180 degrees apart.
Metric Length Conversion
A meter has been officially defined to be the distance traveled by light in a vacuum in 1/299,792,458 second. All other length and distance measurements in the metric system derive from the meter (eg. km= 1000m, 1m= 1000mm).
Imperial / American measurements These measurements have a less logical progression. A yard can be defined as the length of a pendulum that causes its arc to swing in exactly 1 second. The Nautical mile is the distance across 1′ (1/60 of a degree) around the earths surface.
Metric Area Conversion
Metric area measurements are based on the meter, with the main unit being a Hectare, 10000m2.There are exactly 640 acres in a square mile.
Imperial / American measurements: These area measurements are mostly square versions of their linear conterparts except for the acre which is an area of length 1 furlong and a width of 1 chain. The Old English word “acre” means field and it was generally considered the area that could be ploughed in a day using a yoke or oxen.