mathjs/docs/datatypes/units.md

Units

Math.js supports units. Units can be used to do calculations and to perform conversions.

API

Units can be created using the function math.unit. This function accepts either a single string argument containing a value and unit, or two arguments, the first being a numeric value and the second a string containing a unit. Most units support prefixes like k or kilo, and many units have both a full name and an abbreviation. The returned object is a Unit.

Syntax:

math.unit(value: number, name: string) : Unit
math.unit(unit: string) : Unit
math.unit(unit: Unit) : Unit

Example usage:

var a = math.unit(45, 'cm');        // Unit 450 mm
var b = math.unit('0.1 kilogram');  // Unit 100 gram
var c = math.unit('2 inch');        // Unit 2 inch

A Unit contains the following functions:

• clone(). Clone the unit, returns a new unit with the same parameters.
• equalBase(unit). Test whether a unit has the same base as an other unit: length, mass, etc.
• equals(unit). Test whether a unit equals an other unit. Units are equal when they have the same base and same value when normalized to SI units.
• to(unitName). Convert the unit to a specific unit name. Returns a clone of the unit with a fixed prefix and unit.
• toNumber(unitName). Get the value of a unit when converted to the specified unit (a unit with optional prefix but without value).
• format([precision]). Get a string representation of the unit. The function will determine the best fitting prefix for the unit. If precision is defined, the units value will be rounded to the provided number of digits.
• toString(). Get a string representation of the unit. The function will determine the best fitting prefix for the unit.

var a = math.unit(55, 'cm');        // Unit 550 mm
var b = math.unit('0.1 kilogram');  // Unit 100 gram
var c = math.unit('2 inch');        // Unit 100 millimeter

var d = c.to('cm');                 // Unit 5.08 cm
b.toNumber('gram');                 // Number 100

c.equals(a);                        // false
c.equals(d);                        // true
c.equalBase(a);                     // true
c.equalBase(b);                     // false

d.toString();                       // String "5.08 cm"

Calculations

Basic operations add, subtract, multiply, and divide can be performed on units. Trigonometric functions like sin support units with an angle as argument.

var a = math.unit(45, 'cm');        // Unit 450 mm
var b = math.unit('0.1m');          // Unit 100 mm
math.add(a, b);                     // Unit 0.65 m
math.multiply(b, 2);                // Unit 200 mm

var c = math.unit(45, 'deg');       // Unit 45 deg
math.cos(c);                        // Number 0.7071067811865476

Reference

All available units and prefixes are listed on the page Unit reference.