JSFiddle - React, Tailwind, and code Playground
CSS
html {
font-size: 36px;
}
JavaScript
var htmlRoot = document.querySelector('html');
var style = getComputedStyle(htmlRoot);
var remValue = parseInt(style.getPropertyValue('font-size'));
var remValue2 = remValue * 2;
var remValue3 = remValue * 3;
var remValue7 = remValue * 7;