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A module for formatting units in a localized manner

To use

use Intl::Format::Unit;

say format-unit 0,        :unit<length-meter>; # 0 m
say format-unit 1234,     :unit<length-meter>; # 53,425.21 m
say format-unit 53425.21, :unit<length-meter>; # 1,234 m

The sub format-unit takes the following arguments:

  • quantity
    The amount of the unit (a number).
  • unit
    The type of unit (e.g. meter, liter, etc).
  • :language
    The language to use in formatting. Defaults to user-language.
  • :length
    Any of long, short or narrow. Defaults to short.
  • :case
    The grammatical case to use (normally only applicable with long length). Defaults to nominative

The units can be quite complex, even to the point of making no sense. Assuming English,

format-unit 12345.6789, :unit<solar-radius-cubic-yottaliter-per-pound-square-millimeter>;
# 12,345.6789 R☉⋅Yl³/lb⋅mm²

Supported units

The units that are generally supported by CLDR's validity/units.xml file. These have been curated a bit to have the following base units:

g-force meter second arc-minute arc-second degree radian revolution acre hectare foot inch mile yard dunam karat gram liter mole percent permille permyriad permillion item portion gallon gallon-imperial bit byte century decade day day-person hour minute month month-person week week-person year year-person ampere ohm volt calorie foodcalorie joule watt-hour electronvolt therm-us british-thermal-unit pound-force newton hertz dot em pixel astronomical-unit fathom furlong light-year mile-scandinavian nautical-mile parsec point earth-radius solar-radius candela lumen lux solar-luminosity carat grain metric-ton ounce ounce-troy pound stone ton dalton earth-mass solar-mass watt horsepower atmosphere inch-ofhg bar meter-ofhg pascal ofhg knot celsius fahrenheit generic kelvin pound-force-foot newton-meter acre-foot bushel cup cup-metric dessert-spoon dessert-spoon-imperial drop dram jigger pinch quart-imperial fluid-ounce fluid-ounce-imperial pint pint-metric quart tablespoon teaspoon barrel

All of these make take the following SI and SI-ish (˟) prefixes:

yotta zetta exa peta tera giga mega kilo hecto deka deci centi milli micro nano pico femto atto zepto yocto exbi˟ pebi˟ tebi˟ gibi˟ mebi˟ kibi˟

Lastly, the following powers are supported:

square cubic

Using the above units, you can combine them in the following way:

  • To prefix, attach directly: millimeter kiloliter
  • To raise to a power, separate the power and the unit by a hyphen: square-foot, cubic-centimeter
  • To multiple two units, separate by a hyphen: watt-hour
  • To divide two units, separate by a hyphenated per: miles-per-hour.

These can combined in almost infinite complexity. The only restriction is that there may only be one -per- (subsequent ones, per TR 35, are ignored).

Also note that the rarer the combination of units that you get, the more likely that non-major languages may not have full support. For Latin-based languages, this might not look terrible, but for others, it means that the fallback versions (all Latin-script) may be inserted.


More so than other modules in the Intl namespace, this module should be considered experimental for the following reasons:

  1. The method of selecting the unit is not intuitive and will likely be changed.
  2. Composed units were only introduced in CLDR v.38 (early 2020) with support for two languages (French and German).
    As of v.38.1 (late 2020), this has not changed. Use caution when attempting to use these, as some languages may end up creating unexpected combinations (like saying liter per minutes instead of liters per minute). This should not affect the most simple units such as meter or liter or even common ones like kilometers per hour.


  • Intl::CLDR
    Houses the data for calculating the counts
  • Intl::UserLanguage
    Determines the default language when not provided
  • Intl::Format::Number
    Formats the quantity as a decimal number
  • Intl::Number::Plural
    Determines the grammatical-ish number to select the correct pattern


  • More tests files (especially for compound units)

Version History

  • v0.2.0
    • Initial support for composed units
  • v0.1.0
    • Initial version

License and Copyright

© 2020-2021 Matthew Stephen Stuckwisch. Licensed under the Artistic License 2.0.


A module for formatting units in a localilzed manner







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