# 2.3: Physical Units

On installing Karamba3D one can specify the family of physical units to be used for input and results. The default option is metric (e.g. meters, centimeters, degree Celsius, Newtons, …) but Karamba3D can also deal with Imperial units (e.g. feet, inch, degree Fahrenheit, kiloponds, …).

{% hint style="info" %}
The set of units to be used can be changed any time by editing the [“karamba.ini”](/troubleshooting/4.3.-miscellaneous-problems/4.1.6-changing-karamba.ini-file.md) file.
{% endhint %}

Depending on the family of units Karamba3D interprets geometric input either as meters or feet. The kind of physical units that components expect to receive shows up in the tool-tip which appears when the mouse pointer hovers over an input-plug.

Changing the type of physical units during the creation of a GH definition may give rise to problems: The help text of Grasshopper components does not change dynamically. Switching from SI to Imperial Units leaves the help text of those components already placed on the canvas unaltered. The interpretation of the input values however changes. Opening a GH definition with a Karamba3D versions with differently set physical units entails the same problem.

Karamba3D comes with databases for predefined cross sections and materials. The properties there are given in SI units. The same applies to physical constants (e.g. “gravity”) defined in the **“karamba.ini”**-file.

Throughout the rest of this manual SI units will be used exclusively in order to ensure good readability. When specific differences exist between using Karamba3D with Imperial Units and SI units, this will be mentioned in the text.


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