Editing Template:Convert/doc (section)

==Units==
The conversion factors and physical constants are sourced [[Module:Convert/documentation/conversion data introduction/doc#Conversion factors and physical constants|here]].

===All units===
{{selfref|See also: [[Template:Convert/list of units]]}}
{{hatnote|Units are case-sensitive: use {{xt|kW}}, not {{!xt|KW}} or {{!xt|kw}}}}
{{Convert/list of units}}

==='per' units: ''kg/ha'', ''miles per gallon''<span class="anchor" id="per"></span>===
When using a slash (<code>/</code>), a unit like <code>kg/ha</code> is recognized as kilograms ''per'' hectare and will be converted in to other mass/area units. A unit in the numerator is not required.
* <code><nowiki>{{convert|1000|kg/ha}}</nowiki></code> → {{convert|1000|kg/ha}}
* <code><nowiki>{{convert|350|/in2}}</nowiki></code> → {{convert|350|/in2}}

Population density (''inhabitants per square mile'') can be converted using
* <code><nowiki>{{convert|10|PD/sqmi|PD/km2}}</nowiki></code> → {{convert|10|PD/sqmi|PD/km2}}

Vehicular fuel efficiency, commonly expressed in ''miles per gallon'' or ''litres per 100 km'' can also be converted
* <code><nowiki>{{convert|26|mpgUS|l/100km mpgimp}}</nowiki></code> → {{convert|26|mpgUS|l/100km mpgimp}}

===Units of difference: Expressing a change or difference in temperature<span class="anchor" id="Units of difference"></span>===
We have already discussed standard temperature conversions (°C, °F, K), as shown in these two examples:
* {{#invoke:DemoTemplate|convert|10|C}} (standard temperature conversion)
* {{#invoke:DemoTemplate|convert|10|-|15|C}} (standard temperature range conversion)

When expressing a temperature ''change'' (e.g., "The temperature ''increased'' by 10&nbsp;°C"), or when ''comparing'' temperatures (e.g., "10 to 15&nbsp;°C ''warmer''"), we cannot use the standard temperature units ({{para||C}}, {{para||F}} and {{para||K}}), which refer to points on the respective scale. Instead, we must use one of the following "units of difference": {{para||C-change}}, {{para||F-change}} and {{para||K-change}}.

Compare the following two examples with the two above:

* {{#invoke:DemoTemplate|convert|10|C-change}} increase in temperature
* {{#invoke:DemoTemplate|convert|10|-|15|C-change}} warmer than normal

To produce multiple units in the output:
* {{#invoke:DemoTemplate|convert|10|C-change|F-change K-change}} difference

===Multiple units: ''1 ft 5 in''===
====In input====
Base document {{section link|Module:Convert/documentation/conversion data/doc|Input multiples|nopage=y}} lists options for ''multiple unit input'' (like <code>ft,in</code>). It can catch predefined sets only (units that can be subdivided; e.g., yd into ft):
* <code><nowiki>{{convert|1|yd|2|ft|3|in}}</nowiki></code> → {{convert|1|yd|2|ft|3|in}}
* <code><nowiki>{{convert|2|ft|3|in|cm}}</nowiki></code> → {{convert|2|ft|3|in|cm}}
* <code><nowiki>{{convert|1|lb|5|oz|g}}</nowiki></code> → {{convert|1|lb|5|oz|g}}

====In output====
Available multiple-unit output options predefined, like <code>ftin</code> and <code>ydftin</code>. The full list is at {{section link|Module:Convert/documentation/conversion data/doc|Output multiples|nopage=y}}.
* <code><nowiki>{{convert|2|m|ftin}}</nowiki></code> → {{convert|2|m|ftin}}
* <code><nowiki>{{convert|2|m|ft in}}</nowiki></code> → {{convert|2|m|ft in}}, using a space, returns the decimal point
Default behavior, for comparison:
* <code><nowiki>{{convert|2|m}}</nowiki></code> → {{convert|2|m}}

See also:
* {{tl|hands}} a length used to measure horses
* {{tl|Long ton}} a weight in ton, cwt, qr and lb
<!-- todo: mention the 0-3 limits -->

===Currency per unit: ''$/mi &rarr; $/km''===
Using currency symbols in a ''$ per unit'' value, you can convert the per-unit:
* <code><nowiki>{{convert|3.39|$/USgal|$/L}}</nowiki></code> → {{convert|3.39|$/USgal|$/L}}
* <code><nowiki>{{convert|10000|€/ha|€/acre}}</nowiki></code> → {{convert|10000|€/ha|€/acre}}
* <code><nowiki>{{convert|10|¢/mi|¢/km}}</nowiki></code> → {{convert|10|¢/mi|¢/km}}
* <code><nowiki>{{convert|1500|¥/lb|¥/kg}}</nowiki></code> → {{convert|1500|¥/lb|¥/kg}}

You can also set the currency in ''both'' values using {{para|$|€}}:
* <code><nowiki>{{convert|10|$/mi|$/km|$=€}}</nowiki></code> → {{convert|10|$/mi|$/km|$=€}}

It is ''not'' possible to convert the currency:
* <code><nowiki>{{convert|10|$/lb|€/kg}}</nowiki></code> → {{convert|10|$/lb|€/kg}} {{nay}}

So, this result (mixed currencies) is ''not'' possible: {{!mxt|1=$15 per mile (€8.6/km)}} {{nay}}