rem-to-px cli program which you can put in your package.json. It replaces rem with px.
We use this to fix wordpress styling in the admin because all font-sizes of our template looks off.
npm install https://github.com/web-ridge/rem-to-px --save-dev
or
yarn add https://github.com/web-ridge/rem-to-px --dev
We are using this in our "scripts" in our projects like this
node node_modules/rem-to-px --file ./assets/css/editor-style-block.css --multiplier 10
Multiplier of 10 takes care of e.g. 1.5rem to 15px;