convert-units

A handy utility for converting between quantities in different units.

Installation

npm install convert-units --save

# beta builds are also available with
npm install convert-units@beta --save

Usage

convert-units has a simple chained API that is easy to read. It can also be configured with the measures that are packaged with it or custom measures.

The code snippet below shows everything needed to get going:

// `allMeasures` includes all the measures packaged with this library
import configureMeasurements, { allMeasures } from 'convert-units';

const convert = configureMeasurements(allMeasures);

It's also possible to limit the measures configured to only the ones your application needs:

import configureMeasurements, { volume, mass, length } from 'convert-units';

/*
  `configureMeasurements` is a closure that accepts a directory
  of measures and returns a factory function (`convert`) that uses
  only those measures.
*/
const convert = configureMeasurements({
    volume,
    mass,
    length,
});

Here's how you move between the metric units for volume:

convert(1).from('l').to('ml');
// 1000

Jump from imperial to metric units the same way:

convert(1).from('lb').to('kg');
// 0.4536... (tested to 4 significant figures)

Just be careful not to ask for an impossible conversion:

convert(1).from('oz').to('fl-oz');
// throws -- you can't go from mass to volume!

You can ask convert-units to select the best unit for you. You can also optionally explicitly exclude orders of magnitude or specify a cut off number for selecting the best representation.

convert(12000).from('mm').toBest();
// { val: 12, unit: 'm', plural: 'Meters' } (the smallest unit with a value above 1)

convert(12000).from('mm').toBest({ exclude: ['m'] });
// { val: 1200, unit: 'cm', plural: 'Centimeters' } (the smallest unit excluding meters)

convert(900).from('mm').toBest({ cutOffNumber: 10 });
// { val: 90, unit: 'cm', plural: 'Centimeters' } (the smallest unit with a value equal to or above 10)

convert(1000).from('mm').toBest({ cutOffNumber: 10 });
// { val: 100, unit: 'cm', plural: 'Centimeters' } (the smallest unit with a value equal to or above 10)

// by default the system of the origin is used, the `system` option overwrites this behaviour
convert(254).from('mm').toBest({ system: 'imperial' }); // ('mm' is metric)
// { val: 10, unit: 'in', plural: 'Inches' }            // ('in' is imperial)

You can get a list of the measures available to the current instance with .measures

convert().measures();
// [ 'length', 'mass', 'volume', ... ]

const differentConvert = configureMeasurements({
    volume,
    mass,
    length,
    area,
});
differentConvert().measures();
// [ 'length', 'mass', 'volume', 'area' ]

If you ever want to know the possible conversions for a unit, just use .possibilities

convert().from('l').possibilities();
// [ 'ml', 'l', 'tsp', 'Tbs', 'fl-oz', 'cup', 'pnt', 'qt', 'gal' ]

convert().from('kg').possibilities();
// [ 'mcg', 'mg', 'g', 'kg', 'oz', 'lb' ]

You can also get the possible conversions for a measure:

convert().possibilities('mass');
// [ 'mcg', 'mg', 'g', 'kg', 'oz', 'lb', 'mt', 't' ]

You can also get the all the available units:

convert().possibilities();
// [ 'mm', 'cm', 'm', 'in', 'ft-us', 'ft', 'mi', 'mcg', 'mg', 'g', 'kg', 'oz', 'lb', 'mt', 't', 'ml', 'l', 'tsp', 'Tbs', 'fl-oz', 'cup', 'pnt', 'qt', 'gal', 'ea', 'dz' ];

To get a detailed description of a unit, use describe

convert().describe('kg');
/*
  {
    abbr: 'kg',
    measure: 'mass',
    system: 'metric',
    singular: 'Kilogram',
    plural: 'Kilograms',
  }
*/

To get detailed descriptions of all units, use list.

convert().list();
/*
  [{
    abbr: 'kg',
    measure: 'mass',
    system: 'metric',
    singular: 'Kilogram',
    plural: 'Kilograms',
  }, ...]
*/

You can also get detailed descriptions of all units for a measure:

convert().list('mass');
/*
  [{
    abbr: 'kg',
    measure: 'mass',
    system: 'metric',
    singular: 'Kilogram',
    plural: 'Kilograms',
  }, ...]
*/

Custom Measures

It's possible to define custom measures if the ones packaged aren't what you need:

import configureMeasurements from 'convert-units';

const customMeasure = {
  systems: {
    A: {
      a: {
        name: {
          singular: 'a',
          plural: 'as',
        },
        // to_anchor: The factor used to reach the base unit
        // The base unit should have a to_anchor value of 1
        // Eg. 1 a -> al = 1a * 1e-1 (to_anchor of al) = 10 al
        to_anchor: 1,
      },
      al: {
        name: {
          singular: 'al',
          plural: 'als',
        },
        to_anchor: 1e-1,
      },
    },
    B: {
      b: {
        name: {
          singular: 'b',
          plural: 'bs',
        },
        to_anchor: 1,
      },
      bl: {
        name: {
          singular: 'bl',
          plural: 'bls',
        },
        to_anchor: 1e-1,
      },
    },
    C: {
      c: {
        name: {
          singular: 'c',
          plural: 'cs',
        },
        to_anchor: 1,
      },
      cl: {
        name: {
          singular: 'cl',
          plural: 'cls',
        },
        to_anchor: 1e-1,
      },
    },
  },
  anchors: {
    A: {
      // unit a -> unit b
      B: {
        ratio: 2,
      },
      // unit a -> unit c
      C: {
        ratio: 3,
      },
    },
    B: {
      // unit b -> unit a
      A: {
        ratio: 1 / 2,
      },
      // unit b -> unit c
      C: {
        ratio: 3 / 2,
      },
    },
    C: {
      // unit c -> unit a
      A: {
        ratio: 1 / 3,
      },
      // unit c -> unit b
      B: {
        ratio: 2 / 3,
      },
    },
  },
};

const convert = configureMeasurements({ customMeasure });
convert(1).from('a').to('bl')
// 20

The order of opperations goes as follows:

// a -> bl
let v = 1  // 1 a
let a_to_anchor = 1  // systems.A.a.to_anchor
let r = v * a_to_anchor
// r = 1 a
let ratio = 2  // anchors.A.B.ratio
r *= ratio
// r = 2 b
let bl_to_anchor = 1e-1  // systems.B.bl.to_anchor
r /= b_to_anchor
// r = 20 bl

It's also possible to extend existing measures:

import configureMeasurements, {
  length,
  LengthSystems,
  LengthUnits,
  Measure
} from 'convert-units';

type NewLengthUnits = LengthUnits | 'px';
const DPI = 96;
const extendedLength: Measure<LengthSystems, NewLengthUnits> = {
  systems: {
    metric: {
      ...length.systems.metric,
      px: {
        name: {
          singular: 'Pixel',
          plural: 'Pixels',
        },
        to_anchor: 0.0254 / DPI,
      },
    },
    imperial: {
      ...length.systems.imperial,
    },
  },
  anchors: {
    ...length.anchors,
  },
};

const convert = configureMeasurements<'length', LengthSystems, NewLengthUnits>(
  { length: extendedLength }
);

convert(4).from('cm').to('px');
// 151.18110236220474

Migrating from Old API

This only applies if moving from <=2.3.4 to >=3.x.

index.js

import convert from 'convert-units';

convert(1).from('m').to('mm');
convert(1).from('m').to('ft');

The code above could be changed to match the following:

index.js

import convert from './convert';  // defined below

convert(1).from('m').to('mm');
convert(1).from('m').to('ft');

convert.js

import configureMeasurements, { allMeasures } from 'convert-units';

export default configureMeasurements(allMeasures);

Typescript

Defining types can provide the benefit of exposing issues while working on your application.

import configureMeasurements, {
  AllMeasures,
  allMeasures,
  AllMeasuresSystems,
  AllMeasuresUnits,
  area,
  AreaSystems,
  AreaUnits,
  length,
  LengthSystems,
  LengthUnits,
} from 'convert-units';

// Meausres: The names of the measures being used
type Measures = 'length' | 'area';
// Systems: The systems being used across all measures
type Systems = LengthSystems | AreaSystems;
// Units: All the units across all measures and their systems
type Units = LengthUnits | AreaUnits;
const convert = configureMeasurements<Measures, Systems, Units>({
  length,
  area,
});

convert(4).from('m').to('cm');
// 400

// If you'd like to use all the packages measures that can be done like so
const convertAll = configureMeasurements<
  AllMeasures,
  AllMeasuresSystems,
  AllMeasuresUnits
>(allMeasures);

convertAll(4).from('m2').to('cm2');
// 400000

Request Measures & Units

All new measures and additional units are welcome! Take a look at src/definitions to see some examples.

Packaged Units

Length

nm
μm
mm
cm
m
km
in
yd
ft-us
ft
fathom
mi
nMi

Area

Mass

Volume

mm3
cm3
ml
l
kl
m3
km3
tsp
Tbs
in3
fl-oz
cup
pnt
qt
gal
ft3
yd3

Volume Flow Rate

mm3/s
cm3/s
ml/s
cl/s
dl/s
l/s
l/min
l/h
kl/s
kl/min
kl/h
m3/s
m3/min
m3/h
km3/s
tsp/s
Tbs/s
in3/s
in3/min
in3/h
fl-oz/s
fl-oz/min
fl-oz/h
cup/s
pnt/s
pnt/min
pnt/h
qt/s
gal/s
gal/min
gal/h
ft3/s
ft3/min
ft3/h
yd3/s
yd3/min
yd3/h'

Temperature

Time

ns
mu
ms
s
min
h
d
week
month
year

Frequency

Hz
mHz
kHz
MHz
GHz
THz
rpm
deg/s
rad/s

Speed

m/s
km/h
mph
knot
ft/s

Pace

s/m
min/km
s/ft
min/mi

Pressure

Pa
hPa
kPa
MPa
bar
torr
psi
ksi

Digital

Illuminance

lx
ft-cd

Parts-Per

Voltage

Current

Power

W
mW
kW
MW
GW
PS
Btu/s
ft-lb/s
hp

Apparent Power

Reactive Power

VAR
mVAR
kVAR
MVAR
GVAR

Energy

Reactive Energy

VARh
mVARh
kVARh
MVARh
GVARh

Angle

deg
rad
grad
arcmin
arcsec

Charge

Force

Acceleration

g (g-force)
m/s2

Pieces

pcs
bk-doz
cp
doz-doz
doz
gr-gr
gros
half-dozen
long-hundred
ream
scores
sm-gr
trio

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

SteveVanOpstal/convert-units