Board Thread:Support Requests - Getting Technical/@comment-6005769-20150820145019/@comment-4731443-20150820155305

That shouldn't be a problem using. I suggest reading up in this order:
 * 1) Help:Templates for how they work in general
 * 2) Help:Template_parameters for how to set and use variables
 * 3) Parser Functions (specifically #expr)

Your bottom line may eventually look like this: Total weight: kg