UnitConverter

UnitConverter converts between bits/bytes, time, and area, distance, mass, temperature, and volume (and cubic volume) in metric and U.S. Standard units for a total of 175 units providing over 4 thousand unit conversions.

Plus, it allows additional units to be defined (for example, currency) and cross-conversions to be defined between the unit systems. Cross-conversion are not limited to conversion factors, they can be functions if necessary.

Linear Conversion Example in JavaScript

// Example: Calculate the cost of driving.
var unitConv = new UnitConverter();
// Turn on verbose output.
UnitConverter.verbose = true;
// Define U.S. dollars as a base unit since currency is not in the library.
UnitConverter.defineBaseUnit( "US$" );
// Set a factor of 24 miles/gallon.
unitConv.setCrossFactor( 24, "mile", "gallon" );
// Set a factor of 3.349 US$/gallon.
unitConv.setCrossFactor( 3.349, "US$", "gallon" );
// Check whether a conversion is possible.
if( unitConv.canConvert( "mile", "US$" ))
{
	// Convert 300 miles to dollars (~$41.86).
	var cost = unitConv.convert( 300, "mile", "US$" );
}

Non-Linear Conversion Example in JavaScript

var unitConv = new UnitConverter();
// Turn off verbose output.
UnitConverter.verbose = true;
UnitConverter.defineBaseUnit( 'carbon 14', 'time', 'isotope' );
unitConv.setCrossConverter( 
	function carbon_14_percentage_to_years( percentage )
	{
		var half_life = 5730;
		var decay_rate = -0.693;
		var years = (Math.log( percentage ) / decay_rate) * half_life;
		return( years );
	}, 
	'carbon 14', 'year', function years_to_carbon_14_percentage( years )
	{
		var half_life = 5730;
		var decay_rate = -0.693;
		var percentage = Math.exp((years / half_life) * decay_rate );
		return( percentage );
	}
);
if( unitConv.canConvert( 'carbon 14', 'year' ))
{
	var approximate_atoms_per_kilogram_of_an_animal = 1e26;
	var estimated_weight_of_brachiosaurus_kilograms = 5.6e4;
	var one_atom_of_brachiosaurus_percentage = 1 
		/ (approximate_atoms_per_kilogram_of_an_animal 
			* estimated_weight_of_brachiosaurus_kilograms);
	// Convert brachiosaurus remains with one carbon 14 atom to its age (~585405 years).
	var age = unitConv.convert( one_atom_of_brachiosaurus_percentage, 'carbon 14', 'year' );
}

TravisCI