This module can be used to quickly add a new unit for use with {{convert}}. When satisfied that a unit is working correctly, ask at Module talk:Convert for the unit to be moved to the permanent list of units.

See Template:Convert/unit sandbox for a good way to prepare unit definitions that can be copied into this page.

The following extracts from Module:Convert/data show examples that could be used to define a new unit. Any number of spaces can be used where blanks are shown in the following.

Examples for additions to Module:Convert/extra (For the actual module code see below)
-- These are EXAMPLES on the documentation page. Scroll down to see the module content.
local extra_units = {
    -- Similar to a redirect: "sqm" is an alias for "m2".
    -- {{convert|1.5|m2|sp=us}}  → 1.5 square meters (16 sq ft)
    -- {{convert|1.5|sqm|sp=us}} → 1.5 square meters (16 sq ft)
    ["sqm"] = {
        target   = "m2",
    },
    -- A simple unit, showing the minimum that is required.
    -- The "ha" is the unit code used to identify the unit:
    -- {{convert|1.5|ha}} → 1.5 hectares (3.7 acres)
    ["ha"] = {
        name1    = "hectare",
        symbol   = "ha",
        utype    = "area",
        scale    = 10000,
        default  = "acre",
    },
    -- A unit which accepts an SI prefix. There is no "name1" field because it
    -- has to be constructed (mJ gives "millijoule"; MJ gives "megajoule").
    -- {{convert|125|kJ}} → 125 kilojoules (30,000 cal)
    ["J"] = {
        _name1   = "joule",
        _symbol  = "J",
        utype    = "energy",
        scale    = 1,
        prefixes = 1,
        default  = "cal",
        link     = "Joule",
    },
    -- A unit where US and plural names are required.
    -- {{convert|125|cm/s2}} → 125 centimetres per second squared (4.1 ft/s²)
    ["cm/s2"] = {
        name1    = "centimetre per second squared",
        name1_us = "centimeter per second squared",
        name2    = "centimetres per second squared",
        name2_us = "centimeters per second squared",
        symbol   = "cm/s<sup>2</sup>",
        utype    = "acceleration",
        scale    = 0.01,
        default  = "ft/s2",
        link     = "Gal (unit)",
    },
    -- A "per" unit is defined as the ratio of two other units.
    -- {{convert|125|g/cm3}} → 125 grams per cubic centimetre (4.5 lb/cu in)
    ["g/cm3"] = {
        per      = { "g", "cm3" },
        utype    = "density",
        default  = "lb/cuin",
    },
    -- If the automatic "per" link is not wanted, a link can be specified.
    -- {{convert|125|g/cm3|lk=on|disp=unit}} → [[gram]]s per [[cubic centimetre]]
    -- {{convert|125|g/m3|lk=on|disp=unit}} → [[density|grams per cubic metre]]
    ["g/m3"] = {
 per  = { "g", "m3" },
 utype  = "density",
 default  = "lb/cuyd",
 link  = "density",
    },
    -- Characters "$" and "£" are recognized as currency symbols.
    -- {{convert|125|$/acre}} → $125 per acre ($310/ha)
    ["$/acre"] = {
        per      = { "$", "acre" },
        utype    = "cost $ per unit area",
        default  = "$/ha",
    },
    -- An output unit can be defined as a combination of existing units.
    -- {{convert|2|ha|ft2 m2}} → 2 hectares (220,000 sq ft; 20,000 m²)
    -- Any number of output units can be specified.
    -- NOTE: There may be no need to define a combination because a convert
    --       can specify the output by joining unit codes with "+":
    -- {{convert|1.2|acre|ft2+yd2+m2}} → 1.2 acres (52,000 sq ft; 5,800 sq yd; 4,900 m²)
    ["ft2 m2"] = {
        combination = { "ft2", "m2" },
        utype    = "area",
    },
    -- An output unit can be defined using subunits (from least to most significant).
    -- {{convert|90|in|ydftin}} → 90 inches (2 yd 1 ft 6 in)
    ["ydftin"] = {
        combination = { "in", "ft", "yd" },
        multiple = { 12, 3 },
        utype    = "length",
    },
}
Field Description
symbol Unit identifier used when abbr=on is in effect.
name1 Singular name of the unit used when abbr=off is in effect.
name2 Plural name of the unit; not required if it is the same as name1 plus "s".
name1_us Singular name when sp=us is in effect; not required if the same as name1.
name2_us Plural name when sp=us is in effect; not required if the same as name1_us plus "s".
utype Unit type; must be exactly the same as the utype of any other unit used in a conversion.
scale Number of base units in the unit being defined.
default Unit code of the default output used when no output unit is specified in a conversion.
target Unit code of an existing unit (the unit being defined "redirects" to the existing unit).
prefixes Use 1 if an SI prefix is accepted; 2 is used for m2, and 3 is used for m3.
link Article title used when lk=on is in effect; not required if it is the same as name1.


-- Extra conversion data used by Module:Convert.
--
-- [[Module:Convert/data]] defines all units and is transcluded in all pages
-- where [[Module:Convert]] is used. Testing new units by editing that module
-- would invalidate the cache for all affected pages.
--
-- For quick changes and experiments with new units, this module can be edited.
-- Since this module is transcluded in only a small number of pages, changes
-- should cause little server overhead and should propagate quickly.
--
-- If a unit is defined in the data module, any definition here is ignored,
-- so defining the same unit in both modules is not an error.
-- A unit defined here can refer to units that are also defined here, and
-- can refer to units defined in the data module.
--
-- Periodically, those extra units that are wanted permanently can be removed
-- from here after being added to [[Module:Convert/data]].

local extra_units = {
    ["sec"] = {  -- experiment per request at [[Template talk:Convert#Auto-select time unit?]]
	_name1   = "second",
	_symbol  = "s",
	utype    = "time",
	scale    = 1,
	prefixes = 1,
	default  = "v < 7200 ! min ! h",
	link     = "Second",
    },
    ["inches"] = {
	target   = "in",
    },
    ["bit"] = {
	_name1   = "bit",
	_symbol  = "bit",
	utype    = "information",
	scale    = 0.125,
	prefixes = 1,
	default  = "B",
	link     = "Bit",
    },
    ["B"] = {
	_name1   = "byte",
	_symbol  = "B",
	utype    = "information",
	scale    = 8,
	prefixes = 1,
	default  = "bit",
	link     = "Byte",
    },
    ["DW-tonne"] = {
	name1_us = "deadweight metric ton",
	symbol   = "deadweight tonne",
	sym_us   = "~deadweight metric ton",
	usename  = 1,
	utype    = "mass",
	scale    = 1000,
	default  = "DWton",
	link     = "Deadweight tonnage",
    },
    ["hm³"] = {
	target   = "hm3",
    },
    ["MPGE"] = {  -- temporary test for scale 1609.344/(33.705*3.6e6) planned at [[Template talk:Convert#Check arithmetic for MPGe conversion]] ([[Special:PermanentLink/1133610113#Check arithmetic for MPGe conversion|permalink]])
	name1    = "mile per gallon gasoline equivalent",
	name2    = "miles per gallon gasoline equivalent",
	symbol   = "mpg&#8209;e",
	utype    = "energy per unit length",
	scale    = 1.3263314048360777e-5,
	invert   = -1,
	iscomplex= true,
	default  = "kWh/100 mi",
	link     = "Miles per gallon gasoline equivalent",
    },
}

return { extra_units = extra_units }