Step 1 - Do some research and admit that the Metric System of weights and measures is in fact mathematically and economically superior, and that it sucks how most American consumers still don't prefer it - because if they did the businesses would obviously switch. Set aside a tiny fraction of your online time to research the issue further and debate it with others.
Step 2 - Use something like Google to check if there's an existing libertarian strategy for promoting the Metric System without resorting to government force. If you can find one, feel free to borrow some ideas. If you don't, feel free to initiate your own, which is exactly what the author of this forum post is now doing.