UnitsML

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Get Started ​

Everything you need to start using UnitsML in your projects — whether you're encoding units in XML, browsing schemas, or integrating the units database programmatically.

Choose your path ​

XML Encoding

Use UnitsML schemas to encode units in your XML documents.

Browse Schemas

Explore schema definitions interactively at schema.unitsml.org.

Programmatic Access

Use the unitsml-ruby gem to query UnitsDB from your applications.

XML Encoding ​

The UnitsML XML Schema defines how to encode units of measure in XML documents. Here's how to get started:

1. Reference the schema ​

Add the UnitsML namespace to your XML document:

xml
<YourDocument
  xmlns:unitsml="https://schema.unitsml.org/unitsml/1.0"
  xsi:schemaLocation="https://schema.unitsml.org/unitsml/1.0
    https://schema.unitsml.org/unitsml/unitsml-v1.0.xsd">

2. Define a unit ​

xml
<unitsml:UnitSet>
  <unitsml:Unit xml:id="m" dimensionURL="#L">
    <unitsml:UnitName>metre</unitsml:UnitName>
    <unitsml:UnitSymbol>SI</unitsml:UnitSymbol>
  </unitsml:Unit>
</unitsml:UnitSet>

3. Use the unit in your data ​

xml
<Measurement>
  <Value unitsml:unit="#m">9.81</Value>
  <Description>Gravitational acceleration</Description>
</Measurement>

TIP

UnitsML is designed to be incorporated into other markup languages, not used standalone. The models work best when embedded in domain-specific formats like MatML, CML, or your own vocabulary — and can also be expressed in JSON, YAML, and other formats.

Browse Schemas ​

The interactive schema browser provides documentation for all UnitsML schema components:

schema.unitsml.org

Browse element definitions, type hierarchies, and schema documentation for all versions.

Open browser

Programmatic Access ​

Use the unitsml-ruby gem to query UnitsDB from Ruby applications:

Install ​

bash
gem install unitsml-ruby

Query units ​

ruby
require 'unitsml'

# Find a specific unit
unit = Unitsml::Units.find("m")
puts unit.name    # => "metre"
puts unit.symbol  # => "m"

See the unitsml-ruby page for full API documentation.

Next steps ​