# How to set UnitSystem permanently

I would like to set the system of units ($UnitSystem) permanently to "Metric". I know that I can do $UnitSystem = "Metric"


Or use the option UnitSystem -> "Metric", but I would like that change to be permanent and be there when the next session is started.

SetOptions[$FrontEnd, UnitSystem -> "Metric"]  Does not solve the problem (and by the way now I have a meaningless permanent option for $FrontEnd that I don't know how to remove).

• Why not put that in init.m? – J. M.'s ennui Jun 8 '16 at 13:43
• Why go against the flow - imperial units are bound to make a comeback. This metric thing is just a fad :-) – Jason B. Sep 16 '16 at 1:21

I'm on "10.0 for Mac OS X x86 (64-bit) (December 4, 2014)", but the action should not differ for other systems substantially. Nevertheless, a backup is indicated with every system manipulation.

Find the default unit system:

$UnitSystem  Imperial The base directory in which user-specific files are placed: $UserBaseDirectory

/Users/xxxx/Library/Mathematica


And the files within this Directory:

FileNames["*", "/Users/xxxx/Library/Mathematica"] // Column

{
{"/Users/xxxx/Library/Mathematica/ApplicationData"},
{"/Users/xxxx/Library/Mathematica/Applications"},
{"/Users/xxxx/Library/Mathematica/FrontEnd"},
{"/Users/xxxx/Library/Mathematica/Kernel"},
{"/Users/xxxx/Library/Mathematica/Licensing"},
{"/Users/xxxx/Library/Mathematica/Logs"},
{"/Users/xxxx/Library/Mathematica/Paclets"},
{"/Users/xxxx/Library/Mathematica/SystemFiles"}
}


Find all init.mwithiun this Directory:

initFiles = FileNames["init.m", $UserBaseDirectory, Infinity]  {"/Users/xxxx/Library/Mathematica/Applications/WSMLink/Kernel/init.\ m", "/Users/xxxx/Library/Mathematica/FrontEnd/init.m", \ "/Users/xxxx/Library/Mathematica/Kernel/init.m"}  Your User Mathematica initialization file FilePrint@Last@initFiles  Will show in the same *.nb the following: (** User Mathematica initialization file **)$UnitSystem = "Metric"


What to do: