Unit Names in Calchemy

The unit names and abbreviations recognized by the Web version of Calchemy are indexed by category in the Unit Definitions frame or page. Names and abbreviations separated by commas (on the same line) refer to the same unit definition and are case sensitive.

Each of these units may be used in any combination with others to form compound units at will. For instance to enter a speed like "75 miles per hour" you could type "75 miles/hour" or "75 mi/hr" or use the defined abbreviation "75 mph". Compound units can be as complex as you need, like "(kg(m/s)^2)/fortnight". You can even mix units from different systems like "bushel/hectare" or "kg/ft^3".
NOTE, you will not see compound units (like newton/m^2) in the lists of defined units because they are derived, not defined. However derived units with their own names (like Pa) are listed.


Calchemy implements SI prefix rules, including all of the SI prefix names and abbreviations. For example "mg" is the combination of "m" for "milli" and "g" for "gram", not a separately defined unit. As a result you may also express the unit as milligram, milli gram, m gram or even millig.
NOTE, again you will not see prefixed units in the lists of defined units as they are unit modifiers.

Pluralization of units

Calchemy implements a basic set of pluralization rules that are applied to the interpretation of unit names. For instance you may use the plural "miles" instead of "mile", "feet" instead of "foot" or even "henries" instead of "henry". In general Calchemy does not accept plural forms of abbreviations.

Secondary Definitions or "Overloaded units"

Some unit names traditionally have more than one common use, such as "ounce", which can be a unit of mass, force, or volume. We call these "overloaded units". In most cases you may use the traditional name and Calchemy will make a determination of what you mean based on a dimensional analysis of the equation. Calchemy accepts four different overloaded units, they are "pound, lb", "gram, g", "ton", and "ounce, oz". They all may be either mass or force, ounce may also be a volume. If you want to be explicit use an "m", "f", at the end of the unit name to specify mass or force, ie: "poundm" or "poundf". To specify "ounce volume" you may use "floz".

Free Units

"Free units" are units that are not actually understood by Calchemy, except that they are new and unique dimensions which must cancel out in the end. For example in the equation:
2000 lbf * 60 mph / 4 wheels ? hp/wheel
= 80 hp/wheel
wheel is a free unit which Calchemy accepts because it cancels out. The acceptance of free units makes using Calchemy more intuitive.

Physical Properties

In Calchemy you can specifiy certain physical properties of materials using the following conventions to identify the property and the material: (xxx identifies the material, so the density of water would be dens_water)
  dens_xxx  identifies the mass density
  hfm_xxx   identifies the heat of fusion by mass
  hfv_xxx   identifies the heat of fusion by volume
  hvm_xxx   identifies the heat of vaporization by mass
  hvv_xxx   identifies the heat of vaporization by volume
  hcm_xxx   identifies the heat of combustion by mass
  hcv_xxx   identifies the heat of combustion by volume 
  hsm_xxx   identifies the specific heat by mass
  hsv_xxx   identifies the specific heat by volume
  ss_xxx    identifies the speed of sound
  tc_xxx    identifies the thermal conductivity
  te_xxx    identifies the thermal coefficient of expansion
  visc_xxx  identifies the viscosity
The Windows version of Calchemy contains several lists of unit definitions including the physical properties of many materials, obscure units (like barleycorns etc.), properties of the solar system, energy content of fuels etc. In addition, in the Windows version you can add your own unit definitions and unit name abbreviations.

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Last Updated 6/21/2009
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